Blood Pressure

Pulse pressure: what the gap between your two numbers means

Subtract the bottom number from the top one and you’ve got your pulse pressure. Here’s what the gap is thought to show, why two sources disagree about where healthy ends, and why the pattern most people search for is the rare one after 65.

NK Medically reviewed by Dr Nouman Kazmi, MBBS FCPS ·9 min read

Key Takeaways

  • Pulse pressure is one subtraction. The Mayo Clinic answer page published by Augusta Health has it as the top number minus the bottom number, so a resting 120/80 gives you 40.
  • Where “healthy” ends isn’t settled between the two pages this article cites, and the difference matters. That Mayo page calls 40 healthy and says anything above 40 mmHg generally isn’t. The CV Physiology teaching page, which lists the Cardiovascular Physiology Concepts textbook among its companion texts, gives 40 to 50 mmHg as the typical range for the aorta.
  • The two aren’t measuring the same artery, so the figures can’t simply be laid side by side. CV Physiology’s 40 to 50 describes the aorta, and the same page notes that as the pulse travels outward the systolic pressure rises and the diastolic falls, so the gap your cuff reads at the upper arm is the larger one. Neither page sets out to square the two numbers, and this one won’t either.
  • Above a gap of 60, the Mayo page says, pulse pressure is considered a risk factor for cardiovascular disease, particularly in older adults, and stiffness of the aorta is the leading cause of a wider gap as people age.
  • If you searched for a high bottom number with a low top one, it’s uncommon after 65. Of the 5,776 Cardiovascular Health Study participants aged 65 and over who had a baseline reading, 28 had that pattern, and the paper left them out. Among the 3,495 who reached its final analysis, 1,838 had it the other way round.
  • No one’s gap should be judged on a single reading. The British Heart Foundation says blood pressure naturally goes up and down through the day and night, which means both numbers you’re subtracting are moving. Six to eight weeks of them is a trend; one morning is arithmetic.
In This Article
  1. The subtraction, and what it’s called
  2. The pattern people ask about is the rare one
  3. A wide gap, and the two numbers that disagree
  4. When the bottom number is the low one
  5. Common questions
  6. The bottom line

The NHS explains that a reading is given as two numbers with the first higher than the second. The British Heart Foundation explains what each one measures, systolic while the heart is pumping and diastolic while it relaxes between beats. Neither page does the subtraction. The quantity that comes out of it has a name, a normal range and a risk threshold, and you’ll have to go elsewhere to find them.

The subtraction, and what it’s called

The Mayo Clinic content published by Augusta Health gives it in one line: the top number minus the bottom number is the pulse pressure. A resting reading of 120/80 mmHg makes a pulse pressure of 40.

So 138/78 is a gap of 60. A reading of 150/70 is a gap of 80. It’s arithmetic, not a test, and you can do it with any reading you’ve already written down. You don’t need a new device for it.

What the gap describes is the swing. The CV Physiology teaching page, which lists Cardiovascular Physiology Concepts and Normal and Abnormal Blood Pressure as its companion texts, sets out the mechanics: when the left ventricle pushes blood into the aorta the pressure there rises to its maximum, which is the systolic pressure, and as the ventricle relaxes and refills the aortic pressure falls to its lowest point, which is the diastolic. The difference between them is the aortic pulse pressure. Your top number is the peak of each beat and your bottom number is the floor between beats, so the gap is how far the pressure in your arteries travels on every single beat, all day.

Worth doing once, not every morning

Work the gap out from a reading you’ve taken properly, sitting, rested and at the same time of day, and then leave it alone for a few weeks. A single pulse pressure is two moving numbers subtracted from each other, so it moves with both of them. The shape over a couple of months is the part you can do something with.

Understanding
The Complete Guide to Understanding Blood Pressure (UK)
28 of 5,776
is how many adults aged 65 and over had a high bottom number with a top number under 140, among the Cardiovascular Health Study participants who had a baseline reading. The 2017 analysis in the International Journal of Cardiology lists that group among the ones it excluded, at n=28, and that’s all it says about them. It doesn’t give a reason; its own subject is a comparison of two other patterns. Of the 3,495 who reached the final analysis, 1,838 had the mirror image, a top number of 140 or more alongside a bottom number under 90. This was a US community cohort recruited between 1989 and 1993, so it’s a sense of how rare the pattern is rather than a UK prevalence figure.

The pattern people ask about is the rare one

A high bottom number next to a low or normal top one has a clinical name, isolated diastolic hypertension, and it’s a reasonable thing to wonder about. It’s also, in this age group, the pattern the Cardiovascular Health Study counted and then set aside.

It shows up in the methods section of a 2017 International Journal of Cardiology paper by Tsimploulis and colleagues, which worked from the Cardiovascular Health Study. Of the 5,795 participants in the public dataset, 5,776 had a baseline reading. From those, the authors excluded 821 whose diastolic was under 60, and 28 with a diastolic of 90 or more alongside a systolic under 140. Twenty-eight people. The paper doesn’t say why it set them aside, only that it did. It compares two other patterns.

What the same cohort had plenty of was the opposite shape. Of the 3,495 people who made it into the final analysis, 1,838 had isolated systolic hypertension, a systolic of 140 or more with a diastolic under 90, and 240 had both numbers raised together. The cohort’s mean age was 73.

That 1,838 is itself an undercount of the shape. The 821 people with a diastolic under 60 were removed before the final cohort was drawn, and some of them would have fitted it: an editorial by Mosenkis and Townsend, which comes up again below, notes that in older people a common variant of high blood pressure is a raised systolic with a wide pulse pressure and a normal or even low diastolic.

If the bottom number is the one giving you trouble after 65, it’s much more often because it’s drifted down while the top one climbed than because it’s climbed on its own. That widens the gap.

The same study answers a related question: which of the two numbers matters more. Over 13 years of follow-up, new heart failure turned up in 25% of the isolated systolic group, 22% of those with both numbers raised, and 11% of those without hypertension. Adjusted hazard ratios came out at 1.86 and 1.73 against the no-hypertension group. The authors’ conclusion is that among older adults with hypertension, both patterns carry a similar association with new heart failure. One raised number isn’t the gentler version of two.

Dr Troy Randle, a cardiologist writing for the US health system Virtua, makes the same point from the other direction: systolic and diastolic are independent risk factors, and you can be at risk with a normal systolic and a raised diastolic, or the reverse. His page uses American thresholds rather than the NHS’s, so take the framing and leave the numbers.

A wide gap, and the two numbers that disagree

This is the part where the sources part company.

The Mayo Clinic answer page says a pulse pressure of 40 is healthy and that, generally, a pulse pressure greater than 40 mmHg is unhealthy. CV Physiology says the aortic pulse pressure typically ranges between 40 and 50 mmHg. On the face of it, one of them says 45 is past the healthy line and the other says it isn’t.

The two aren’t measuring the same artery, and CV Physiology says so on its own page. Its 40 to 50 figure is for the aorta. A cuff on your upper arm measures the brachial artery instead, and as the pressure pulse travels out from the aorta into the distributing arteries the systolic rises and the diastolic falls, so the pulse pressure increases the further from the aorta you read it.

The page attributes that to waves reflecting back from vessel branching and to the arteries themselves being less compliant, which is to say stiffer, further out. The gap in your aorta and the gap on your monitor are related but they aren’t the same quantity.

That difference, if anything, pulls the two figures further apart rather than closer: a cuff gap corresponding to CV Physiology’s aortic 40 to 50 would read higher still, and Mayo’s 40 is already a cuff figure. Neither page tries to reconcile them, so read them as two measurements of different things. There is no contradiction to solve.

One figure carries a clear marker, and it’s 60, not 40

The Mayo page says that measuring pulse pressure may help a clinician judge the risk of a heart event, and that a pulse pressure greater than 60 is considered a risk factor for cardiovascular disease, especially in older adults. That 60 comes from the Mayo page on its own: CV Physiology never mentions it. If your readings sit consistently above a 60-point gap, that’s one to raise at your next appointment rather than something to act on at home.

As for what a widening gap is thought to reflect, the Mayo page is specific: stiffness of the aorta is the leading cause of increased pulse pressure in older adults, high blood pressure and fatty deposits on artery walls can both make arteries stiff, and the greater the pulse pressure, the stiffer and more damaged the vessels are thought to be. That last phrase is the page’s own hedge. Pulse pressure is treated as a marker of arterial stiffness, not a measurement of it.

The British Heart Foundation describes the same physical change without the arithmetic. Arteries are normally stretchy, it says, so they can cope with blood pressure going up and down, and with high blood pressure they lose that stretchiness and become stiff or narrow. A gap that widens over years is one way that loss of stretch shows up in numbers you can see at home.

The Mayo page adds that pulse pressure usually narrows again once high blood pressure is being managed, and that the ordinary things still apply: regular exercise, not smoking, limiting alcohol and less salt in the diet.

There’s one reading of the gap this page can’t give you, and it’s the narrow one. None of the sources behind this article covers a gap well below the usual range. The one page that does is a company blog with no named author or institution, which is not something this site cites, so the narrow end is a gap in what’s written here rather than a gap in the subject. It’ll go in when there’s a source worth citing.

Understanding
Normal Blood Pressure by Age: A UK Guide

When the bottom number is the low one

Because a wide gap in an older reader usually means a low-ish diastolic, the next question follows, and it’s how low is too low. There’s no single answer: three of the sources below give three different ones.

The cautious position

An editorial by Mosenkis and Townsend in the Journal of Clinical Hypertension sets out the J-shaped curve, where mortality and coronary events rose in groups whose diastolic ended up below 65 to 85 mmHg. It leans on a 1999 reanalysis of the SHEP trial, which found more cardiovascular events among people with isolated systolic hypertension whose diastolic came in under 70, and roughly double the relative risk below 55. The authors land on watchfulness around 56 to 60 mmHg as the point where risk may start to approach benefit.

What that editorial says about its own evidence

The same editorial sets out how thin the evidence underneath it is, and it doesn’t bury the hedges: they sit right next to the figures. Few patients ever reached a diastolic under 55, the editorial’s own words are that “a careful reading of this study suggests that levels of 45 mm Hg were not deleterious”, the pattern showed up in the treated arm and not the placebo arm, and the event rate in treated people with a low diastolic was still below the event rate in the placebo group.

It also offers three competing explanations for the curve, one of which is that a low diastolic is really standing in for a widened pulse pressure, and therefore for arterial stiffness. On that reading, the gap is the real signal, and the low bottom number is just where it shows up.

Where it stood in 2021

In April 2021 the National Heart, Lung, and Blood Institute reported an analysis of genetic and health data from more than 47,000 adults across five cohorts, median age 60. It found no evidence of raised heart attack risk where diastolic pressure fell as low as 50 mmHg, and no lower limit for what counts as a normal diastolic at all. Many clinicians, it notes, work to keep the bottom reading between 70 and 90, and the researchers suggested some people may have been undertreated as a result.

Pulling against that, there’s a 2011 University of Alabama at Birmingham study in Hypertension, which named the pattern of a diastolic under 60 alongside a systolic above 100 isolated diastolic hypotension, and linked it to a higher risk of new heart failure and of death in older adults. It compared 545 older adults who had it with 2,348 matched adults who didn’t, from the same Cardiovascular Health Study, followed for more than 12 years.

So: a 2004-era editorial urging caution below 60, a 2011 cohort study finding risk below 60, and a 2021 pooled analysis finding no floor down to 50. That isn’t a question a web page gets to close. It’s a question for whoever knows your readings and, if you take tablets for blood pressure, prescribes them. The UAB team said as much in their own words: the difficulty is finding a dose that brings a systolic under 140 without taking the diastolic under 60.

Understanding
Low Diastolic Blood Pressure: What a Low Bottom Number Means

One last thing about the top number, since the gap has two ends. The NHS puts high blood pressure at 140/90 or higher when a healthcare professional checks it, and 135/85 or higher at home. The BHF, on its own page, says that for most people high blood pressure is a reading over 140/95 mmHg, and gives 90/60 to 130/85 as the usual healthy band. Two UK sources, five millimetres of mercury apart on the bottom number. It’s a reminder that these are lines drawn across a continuum rather than edges you fall off.

Matter BP Tracker

A gap is a trend, and a trend needs a record

One subtraction doesn’t tell you much, because both numbers move through the day and night. A run of them over six to eight weeks is a different thing. The Matter BP Tracker keeps each reading with its date and whatever you noted beside it, so you can see the shape of both numbers over time and take something more useful than this morning’s figure to your next appointment.

Open the BP Tracker → Readings and notes·Charted over weeks

Common questions

It’s the difference between your two numbers. The Mayo Clinic answer page published by Augusta Health puts it in one line: the top number (systolic) minus the bottom number (diastolic) is the pulse pressure, so a resting 120/80 mmHg gives a pulse pressure of 40. The CV Physiology teaching page explains what that difference describes. Aortic pressure rises to its maximum as the left ventricle pushes blood out, which is the systolic, and falls to its lowest point as the ventricle relaxes and refills, which is the diastolic. The gap between them is how far the pressure in your arteries swings on every beat.

Two sources give different answers, and they aren’t measuring the same artery. The Mayo Clinic page calls 40 a healthy pulse pressure and says that, generally, a pulse pressure greater than 40 mmHg is unhealthy. CV Physiology gives the aortic pulse pressure as typically ranging between 40 and 50 mmHg. The measurements are taken in different places: CV Physiology’s range is for the aorta, and the same page notes that as the pulse travels outward the systolic rises and the diastolic falls, so the pulse pressure read by a cuff on your upper arm is larger than the one in your aorta. The two gaps can’t be compared directly, and neither page tries to square them. The one figure with a clear marker attached is 60, and it comes from the Mayo page alone: above that, it says, pulse pressure is considered a cardiovascular risk factor.

It’s a number to take to a clinician. The Mayo Clinic page says measuring pulse pressure may help a healthcare provider judge the risk of a heart event such as a heart attack or stroke, and that a pulse pressure greater than 60 is considered a risk factor for cardiovascular disease, especially in older adults. One reading isn’t the test, though. The British Heart Foundation points out that blood pressure naturally goes up and down through the day and night, so a gap worked out from a single morning doesn’t tell you much. A run of readings over six to eight weeks will show you whether it’s genuinely sitting above 60.

It’s read as a sign of stiffer arteries. The Mayo Clinic page says stiffness of the aorta is the leading cause of increased pulse pressure in older adults, that high blood pressure and fatty deposits on the artery walls can both make arteries stiff, and that the greater the pulse pressure, the stiffer and more damaged the blood vessels are thought to be. That hedge matters: it’s treated as a marker of arterial stiffness, not a direct measurement of it. The British Heart Foundation describes the same change without the arithmetic, saying arteries are normally stretchy so they can cope with blood pressure going up and down, and that with high blood pressure they lose that stretchiness and become stiff or narrow.

Yes, and it’s got a name, isolated diastolic hypertension, but past 65 it’s uncommon. The evidence sits in the methods of a 2017 International Journal of Cardiology analysis of the Cardiovascular Health Study: of the 5,776 participants who had a baseline reading, all aged 65 or over at recruitment, just 28 had a diastolic of 90 or more alongside a systolic under 140, and the paper excluded that group. Among the 3,495 who reached the final analysis, 1,838 had the opposite pattern, a systolic of 140 or more with a diastolic under 90. That was a US community cohort recruited between 1989 and 1993, so read it as a sense of how rare the pattern is rather than as a UK prevalence figure.

Genuinely unsettled, and it belongs to whoever knows your readings. An editorial by Mosenkis and Townsend in the Journal of Clinical Hypertension describes the J-shaped curve, with more deaths and coronary events in groups whose diastolic ended up below 65 to 85 mmHg, and settles on watchfulness around 56 to 60. It sets out the thin evidence underneath it: few patients reached a diastolic under 55, a close reading suggested 45 mmHg wasn’t harmful, and treated patients with a low diastolic still had fewer events than the placebo group. A 2011 University of Alabama at Birmingham study linked a diastolic under 60 alongside a systolic above 100 to a higher risk of new heart failure in older adults. Then in 2021 the National Heart, Lung, and Blood Institute reported an analysis of more than 47,000 adults that found no raised heart attack risk down to 50 mmHg and no lower limit of normal at all. If you take tablets for blood pressure, this is one for the person who prescribes them.

The bottom line

Pulse pressure is the top number minus the bottom number, and the Mayo Clinic answer page gives 40 from a resting 120/80 as the healthy example. The figure to remember is 60, because that’s where the same page puts the risk marker for cardiovascular disease in older adults, and a wider gap is read as a sign of a stiffer aorta rather than as a measurement of one.

Where healthy ends isn’t agreed between the two pages cited here, and they aren’t measuring the same artery. CV Physiology’s 40 to 50 range belongs to the aorta, and its own page explains that the gap grows as the pulse travels out towards the arm where your cuff sits, so the two figures end up further apart. One figure in isolation was never going to settle it.

If you came here because your bottom number looks high next to your top one, the Cardiovascular Health Study suggests that combination is uncommon past 65: twenty-eight people among the 5,776 with a baseline reading, a group the paper excluded rather than analysed. The common version of a bottom-number problem in this age group runs the other way, and it shows up as a widening gap. How low a diastolic should go is genuinely unsettled, with a 2021 analysis of more than 47,000 people finding no floor down to 50 and older work urging care below 60.

None of which asks anything of you this week. Take the readings the way you already do, sitting and rested and at a consistent time, write them down, and let eight weeks of them accumulate. Do the subtraction on the trend rather than on a single morning, and if the gap sits above 60 across those weeks, that’s the thing to mention at your next appointment.

Continue Learning

Understanding
The Complete Guide to Understanding Blood Pressure (UK)
Understanding
Low Diastolic Blood Pressure: What a Low Bottom Number Means
Understanding
Normal Blood Pressure by Age: A UK Guide
Measuring
How to Measure Blood Pressure Correctly at Home
Dr Nouman Kazmi
Medically reviewed by Dr Nouman Kazmi Consultant Cardiologist (MBBS, FCPS). Dr Kazmi reviews clinical content on the Matter Heart Health Resource Centre for accuracy.
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References

  1. NHS. High blood pressure (hypertension). Page last reviewed 19 July 2024. Available at: nhs.uk
  2. British Heart Foundation. High blood pressure (hypertension), causes and symptoms. Page updated 31 March 2026. Available at: bhf.org.uk
  3. Tsimploulis A, Sheriff HM, Lam PH, et al. Systolic-diastolic hypertension versus isolated systolic hypertension and incident heart failure in older adults: insights from the Cardiovascular Health Study. Int J Cardiol. 2017 Mar 1;235:11–16. doi:10.1016/j.ijcard.2017.02.139. Available at: pmc.ncbi.nlm.nih.gov
  4. Mosenkis A, Townsend RR. Diastolic blood pressure control: how low is too low? J Clin Hypertens (Greenwich). 6(6):351–352. doi:10.1111/j.1524-6175.2004.02867.x. The PMC record gives a collection date of June 2004. Available at: pmc.ncbi.nlm.nih.gov
  5. National Heart, Lung, and Blood Institute. Study on diastolic blood pressure could change how doctors treat some patients with hypertension. 13 April 2021. Available at: nhlbi.nih.gov
  6. University of Alabama at Birmingham. Low diastolic blood pressure linked to higher risk of heart failure. 26 September 2011, reporting a study published in Hypertension. Available at: uab.edu
  7. CV Physiology. Arterial blood pressure. Revised 6 December 2022. The page names no author; it lists Cardiovascular Physiology Concepts (3rd edn, Wolters Kluwer 2021) and Normal and Abnormal Blood Pressure (Richard E. Klabunde, 2013) as its companion texts. Available at: cvphysiology.com
  8. Mayo Clinic content published by Augusta Health. Pulse pressure: an indicator of heart health? Updated 1 March 2022. Available at: augustahealth.com
  9. Randle T. Get to the bottom of blood pressure numbers. Virtua Cardiology, updated 7 July 2025. Virtua is a US health system and the page uses American blood pressure thresholds. Available at: virtua.org
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