Blood pressure on the leg is most commonly measured at the ankle, where a standard-sized cuff is placed just above the malleoli (the bony bumps) and the pulse is detected over the posterior tibial or dorsalis pedis artery. The calf and thigh are also used, though each site behaves differently and yields readings that do not match what you would get from the arm. Knowing which site to use, and why the numbers come out the way they do, depends on the clinical reason for measuring there in the first place.
The Three Main Sites on the Leg
When clinicians talk about leg blood pressure, they are usually referring to one of three locations: the ankle, the calf, or the thigh. Each has a different purpose and a different track record for accuracy.
- Ankle: The most frequently used leg site, especially for calculating the ankle-brachial index. The cuff wraps around the lower leg just above the ankle bones, and the systolic pressure is detected either by listening with a handheld Doppler probe or by using an oscillometric (automatic) device. This site is foundational to screening for peripheral arterial disease.
- Calf: The cuff sits around the widest part of the mid-calf, and pressure is typically detected over the posterior tibial artery. The calf is sometimes used during surgery or in intensive care when both arms are occupied with IV lines or arterial catheters.
- Thigh: A large cuff is placed around the upper thigh, and pressure is detected at the popliteal artery behind the knee or at the ankle arteries. The thigh site is used mainly in segmental pressure testing, a specialized vascular study designed to locate blockages at different levels of the leg.
A study comparing cuff sites in awake patients found that the calf reading averaged about 4 mmHg higher than the arm, while the ankle ran about 8 mmHg higher. Interestingly, patients rated the calf cuff as the most uncomfortable of the three leg sites and the ankle cuff as the least uncomfortable, leading the authors to suggest the ankle as the preferred alternative when the arm is unavailable.1PubMed. Comparison of blood pressure measured at the arm, ankle and calf
Why Leg Blood Pressure Is Higher Than Arm Blood Pressure
If you measure blood pressure on the leg of a healthy person, the systolic number will almost always be higher than what you get from the arm. In one study, the mean systolic reading at the right calf was about 145 mmHg compared with roughly 123 mmHg in the right arm, a difference of more than 20 points.2Europe PMC. Comparison of arm and calf blood pressure The diastolic gap was smaller but still present.
This is not a measurement error. Pressure naturally amplifies as the pulse wave travels from the aorta into the smaller arteries of the legs. The arteries in the lower body are stiffer and narrower, and when the pulse wave bounces back from these more resistant vessels, it adds to the forward-moving pressure. Gravity and the hydrostatic column of blood also contribute, especially when you are standing. Shifting from lying down to standing can cause a substantial jump in leg blood pressure, which is one reason most vascular measurements are taken with the patient lying flat.3American Journal of Hypertension. Leg Blood Pressure Measured in Orthostatic Posture Is Associated With Left Ventricular Mass in Normotensive Subjects
The practical takeaway is that leg readings should never be directly compared with arm-based blood pressure targets. A systolic reading of 145 at the ankle might be perfectly normal for that site, even though 145 at the arm would suggest hypertension. What matters clinically is the ratio between the two sites or the pattern across multiple leg sites, not the absolute leg number by itself.
The Ankle-Brachial Index
The single most common reason to measure blood pressure on the leg is to calculate the ankle-brachial index, or ABI. You take the highest systolic pressure at the ankle (checking both the posterior tibial and dorsalis pedis arteries) and divide it by the highest systolic pressure from either arm. In a healthy person, that ratio is typically between 1.0 and 1.4, because ankle pressure is naturally a bit higher than arm pressure.
When the ABI drops below about 0.9, it suggests that blood flow to the legs is restricted, usually by atherosclerotic plaques narrowing the arteries. This is peripheral arterial disease, and the ABI is the primary bedside screening tool for it. The gold standard technique uses a handheld Doppler ultrasound probe to listen for the pulse while deflating a cuff at the ankle. An automatic oscillometric device can also measure ankle pressure, and several studies have found a reasonable correlation between oscillometric and Doppler-based readings.4PubMed Central. Ankle blood pressure measured by automatic oscillotonometry: a comparison with Doppler pressure measurements
However, the agreement is not perfect, and it breaks down in exactly the patients who need the test most. One study found no significant agreement between oscillometric and Doppler-derived ABI readings, with substantial variation even between repeated automatic measurements on the same limb.5PubMed. Comparison of ankle-brachial pressure index measurements using an automated oscillometric device with the standard Doppler ultrasound technique Another review found that when the oscillometric device was used alone, it failed to detect ankle systolic pressure in 11 out of 16 cases where patients had very low pressures. Accuracy improved when the oscillometric device was used alongside a Doppler probe, but the authors did not recommend using the oscillometric device by itself for ABI.6Journal of Vascular Brasileiro. Validity, reliability and accuracy of oscillometric devices, compared with Doppler ultrasound, for determination of the Ankle Brachial Index: an integrative review A validation study did find excellent correlation between automatic readings and intra-arterial measurements over a wide pressure range, but the correlation weakened specifically at the lower limbs compared with the upper limbs.7PubMed. Validation of a new method of detecting peripheral artery disease by determination of ankle-brachial index using an automatic blood pressure device
If your doctor measures your ankle pressure with a standard automatic cuff and the result looks normal, that may be accurate enough for a screening visit. But if there is a strong clinical suspicion of arterial disease, or if the automatic device gives an unexpectedly low or high number, a Doppler-based measurement is the more reliable follow-up.
Segmental Pressures and Locating Blockages
When a low ABI suggests arterial disease, vascular specialists can narrow down the location of the blockage by measuring pressures at several levels along the leg. This is called segmental limb pressure testing, and it dates back to 1950, when Winsor first described placing narrow cuffs at the upper thigh, above the knee, below the knee, and at the ankle.8US Cardiology. Principles of Pressure Measurements for Assessment of Lower-extremity Peripheral Arterial Disease – Section: Segmental Limb Pressure A pressure drop of roughly 20 mmHg or more between adjacent levels suggests a significant narrowing in the arterial segment between those two cuffs.
One quirk of this technique is that the upper-thigh cuff has historically produced artificially high readings. Early researchers used a narrow cuff at the thigh, which inflates to higher pressures before it fully compresses the artery, yielding a falsely elevated number. Wider thigh cuffs correct for this, but the principle that cuff width matters to accuracy is the same one that affects arm measurements in anyone with large limbs. The thigh, being a bulky and conical limb, is particularly prone to cuff-sizing issues.
When the Ankle Is Unreliable
The ABI assumes that the ankle arteries can be compressed by the cuff, which is true in most people. But in patients with heavily calcified arteries, the vessel walls become so rigid that the cuff cannot squeeze them shut. The result is a falsely elevated ankle pressure and a misleadingly normal or even high ABI, masking underlying arterial disease. This is a well-recognized problem in people with diabetes and chronic kidney disease, where medial arterial calcification is common.9The Lancet. Diagnostic performance of non-invasive bedside tests for peripheral arterial disease in patients prone to medial arterial calcification: a systematic review and meta-analysis
There are two main workarounds. One is to use diastolic rather than systolic pressure for the ABI calculation. Because the diastolic pressure is less affected by arterial stiffness, a diastolic ABI can still provide useful information when the systolic version is unreliable.10PubMed Central. Diastolic versus systolic ankle-brachial pressure index using ultrasound imaging & automated oscillometric measurement in diabetic patients with calcified and non-calcified lower limb arteries The other is to move the measurement down to the toe. The small digital arteries in the toes are less likely to be calcified, so a toe-brachial index can detect arterial disease that a standard ABI misses.11PubMed Central. Screening for Peripheral Artery Disease Using an Automated Four-Limb Blood Pressure Monitor Equipped with Toe-Brachial Index Measurement The normal threshold for the toe-brachial index is lower than for the standard ABI, typically around 0.7 or above, reflecting the smaller caliber of the toe arteries.
Coarctation of the Aorta
Outside of vascular disease screening, the other classic reason to check leg blood pressure is to diagnose coarctation of the aorta, a congenital narrowing of the aorta that restricts blood flow to the lower body. In a person with coarctation, arm blood pressure is elevated and leg blood pressure is abnormally low, reversing the normal pattern where the leg is higher. This arm-to-leg gradient is one of the key bedside clues to the diagnosis, particularly in children and young adults with unexplained hypertension. All patients with coarctation are at increased risk of hypertension both before and after surgical repair, making long-term follow-up essential.12Hypertension. Coarctation of the Aorta: Modern Paradigms Across the Lifespan
In pediatric practice, checking blood pressure in both an arm and a leg is part of the standard workup for any child with high blood pressure. The measurement is typically taken at the calf or ankle with an appropriately sized pediatric cuff. If the leg pressure is lower than or equal to the arm pressure, rather than higher as expected, further imaging of the aorta is warranted.
Leg Blood Pressure During Surgery and in Critical Care
In the operating room and the intensive care unit, the arms are sometimes simply unavailable. Surgical drapes may cover them, IV lines and arterial catheters may occupy them, or injuries may make arm cuff placement unsafe. In these situations, clinicians often move the blood pressure cuff to the leg.
A study in critically ill patients compared noninvasive cuff readings at the arm, ankle, and thigh against invasive intra-arterial monitoring. The arm cuff was the most accurate for tracking mean arterial pressure, with a mean bias of about 3.4 mmHg. The ankle and thigh cuffs were less precise, with wider limits of agreement. However, during acute circulatory failure, all three leg-and-arm sites performed well at detecting dangerously low pressures and at tracking whether a treatment intervention was working.13Critical Care Medicine. Noninvasive monitoring of blood pressure in the critically ill In other words, the leg sites were less accurate at giving you the exact number, but they were still reliable enough to guide moment-to-moment treatment decisions in an emergency.
During cesarean sections, the story is less reassuring. One study found poor correlation between calf and arm readings in women undergoing the procedure, leading the authors to warn against relying on calf blood pressure to monitor the mother or assess fetal well-being during delivery.14PubMed. Comparison of non-invasive blood pressure measurements on the arm and calf during cesarean delivery The hemodynamic shifts that happen during pregnancy and spinal anesthesia may contribute to this disconnect.
For obese patients undergoing surgery, one study compared multiple cuff sites against an arterial line and found that the forearm actually performed better than both the upper arm and the lower leg for tracking intra-arterial pressure.15Anesthesiology. Intraoperative Blood Pressure Monitoring in Obese Patients The leg was not a bad option, but it was not the best alternative either. Part of the difficulty with obese patients is that limb shape matters as much as limb size when fitting a cuff. A conically shaped limb makes it hard for a standard cylindrical cuff to sit flush, and that poor fit can skew the reading by as much as 10 mmHg.16PubMed Central. Cuff challenges in blood pressure measurement
Getting a Reliable Leg Reading at Home or in a Clinic
Most home blood pressure monitors are designed and validated for the upper arm, and manufacturers rarely test their devices on the leg. If you have been told to check your leg blood pressure at home, there are a few things worth knowing.
First, position matters. Lie flat on your back with the cuff at heart level if possible. Standing will inflate the reading substantially because of the column of blood between the heart and the cuff, and even sitting with the leg dangling can introduce enough hydrostatic pressure to throw off the number. Second, cuff size matters. The bladder inside the cuff should encircle at least 80 percent of the limb’s circumference. A cuff that is too small will overestimate pressure; one that is too large will underestimate it. Calves and thighs vary enormously in girth, so you may need a different size than what came with your monitor. Third, give the first reading less weight. As with arm measurements, the first reading tends to run higher. Taking two or three readings a minute apart and averaging the last two gives a more stable result.
For ABI screening specifically, some pharmacies and vascular clinics offer the test as a quick screening service, using a Doppler probe and ankle cuffs. It takes about 10 to 15 minutes and provides a ratio that is straightforward to interpret: below 0.9 suggests arterial disease, and below 0.5 suggests severe disease. If you have risk factors like smoking, diabetes, or a family history of cardiovascular problems and have never had your ABI checked, it is a reasonable test to ask about.
The Toe as a Measurement Site
The toe is gaining attention as a practical site for blood pressure measurement in specific populations. A small cuff wraps around the great toe, and pressure is detected using a photoplethysmographic sensor or a laser Doppler probe. The toe-brachial index is especially useful in the diabetic population, where calcified ankle arteries can render the standard ABI misleading.11PubMed Central. Screening for Peripheral Artery Disease Using an Automated Four-Limb Blood Pressure Monitor Equipped with Toe-Brachial Index Measurement Some newer four-limb blood pressure devices now include toe pressure measurement as part of an automated screening panel, which makes it easier to incorporate into routine clinical visits without needing a dedicated vascular lab.
Toe pressure has its own limitations. Cold toes can give falsely low readings because vasoconstriction reduces flow. Patients need to be warm and relaxed, and clinicians often wait a few minutes after removing shoes and socks before taking the measurement. Despite these quirks, the toe fills an important gap for the millions of people with diabetes whose ankle readings cannot be trusted.