ABPI calculation (Ankle–Brachial Pressure Index)
Enter systolic pressures in mmHg. Results update instantly and are calculated on your device.
Results
ABPI is calculated per leg using the highest ankle reading and the highest brachial reading.
Right leg
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Enter values to calculate
Left leg
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Enter values to calculate
Worst (lowest) ABPI
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TBPI/TBI note
How to measure ABPI (quick guide)
- Have the person rest supine for 5–10 minutes in a warm room.
- Measure brachial systolic pressure in both arms (if possible) using a Doppler and cuff.
- Measure ankle systolic pressure at the dorsalis pedis (DP) and posterior tibial (PT) arteries for each leg.
- Use the highest ankle pressure for each leg and the highest brachial pressure overall.
- If ABPI seems inconsistent with symptoms, pulses, or Doppler signals, seek further assessment.
Tip: Record which artery gave the highest ankle value (DP or PT). That improves repeatability.
Compression guidance (educational)
Compression decisions should follow local NHS/organisation protocols and a full assessment. The bands below are conservative and educational only.
- ABPI > 0.81: high compression may be suitable (e.g., 30–40 mmHg) depending on full assessment and local policy.
- ABPI 0.80–0.51: modified/reduced compression may be considered only with specialist input and local policy.
- ABPI < 0.50: compression is generally contraindicated; arrange vascular assessment/urgent review as appropriate.
If ABPI is ≥ 1.40 (or diabetes/CKD is present), consider that ABPI can be unreliable and toe pressures (TBPI/TBI) may be used in local pathways.
Disclaimer: This ABPI calculator is for education and quick calculations only. It does not replace clinical judgement, local pathways, or a full vascular assessment.
How this ABPI calculator works
This tool calculates ABPI for the right and left legs using the highest available ankle systolic pressure (DP or PT) and the highest available brachial systolic pressure (either arm). It is designed for quick ABPI calculation in UK clinical and educational contexts.
ABPI formula
ABPI is a ratio of ankle to arm systolic pressure:
ABPI = (highest ankle systolic pressure) ÷ (highest brachial systolic pressure)
How to interpret ABPI results
Interpretation can vary slightly by setting. The bands below are UK-style, intentionally clear, and should be used alongside symptoms, pulses, Doppler signals, and local guidance.
| ABPI range | Interpretation | Educational note |
|---|---|---|
| < 0.50 | Severe arterial disease (urgent vascular review) | High PAD risk. Compression is usually contraindicated until assessed. |
| 0.50–0.79 | Moderate arterial disease | PAD likely. Consider specialist input, especially for wounds/ulcers. |
| 0.80–0.89 | Mild arterial disease | Borderline-low blood flow. Interpret with symptoms and Doppler findings. |
| 0.90–0.99 | Borderline | May be normal for some; consider risk factors and symptoms. |
| 1.00–1.39 | Normal | Typically lower PAD risk, but symptoms still matter. |
| ≥ 1.40 | Possible arterial calcification / incompressible vessels | ABPI may be unreliable; consider TBPI/TBI or further assessment. |
This table is highlighted automatically for each leg when results are available.
FAQs
What is ABPI and what does it measure?
ABPI (ankle–brachial pressure index), sometimes called ABI, compares systolic blood pressure at the ankle with systolic pressure at the arm. It is a quick way to screen for reduced blood flow in the legs, which may suggest peripheral arterial disease (PAD).
How do I calculate ABPI for each leg?
For each leg, use the highest ankle systolic pressure (dorsalis pedis or posterior tibial) and divide it by the highest brachial systolic pressure (from either arm). This calculator does that automatically and rounds the displayed value to 2 decimal places.
Which arm pressure should I use?
Use the higher of the left or right brachial systolic pressures if both are available. If you only have one arm reading, use that. If you have no brachial reading, ABPI cannot be calculated.
Which ankle pressure should I use (dorsalis pedis vs posterior tibial)?
Use the higher ankle systolic pressure for that leg, whether it comes from the dorsalis pedis (DP) or posterior tibial (PT) artery. If you only have one ankle artery reading, you can still calculate ABPI for that leg.
What is a normal ABPI range?
In many UK settings, an ABPI between 1.00 and 1.39 is considered normal. Values just below that can be borderline, and lower values may suggest arterial disease.
What does a low ABPI suggest?
A low ABPI can suggest reduced arterial blood flow in the leg and may be consistent with PAD, particularly if symptoms such as intermittent claudication are present. Always interpret results alongside history, pulses, Doppler findings, and local guidance.
What does a high ABPI (≥ 1.40) suggest?
An ABPI at or above 1.40 may indicate arterial calcification or incompressible arteries, meaning the reading may be unreliable. In this situation, further assessment (such as toe pressures) may be considered.
When might TBPI/TBI be useful?
Toe brachial pressure index (TBPI/TBI) can be useful when ABPI is high (≥ 1.40) or potentially unreliable, such as in diabetes or chronic kidney disease (CKD). Local services may use toe pressures to support vascular assessment and compression decisions.
Can ABPI guide compression therapy for leg ulcers?
ABPI can contribute to decisions about compression therapy for venous or mixed aetiology leg ulcers, but it is not the only factor. Follow local NHS/organisation protocols and consider the whole clinical picture, including symptoms, skin changes, and Doppler signals.
Is ABPI enough on its own?
No. ABPI is a helpful screening and monitoring tool, but it does not replace a full vascular assessment. If results are concerning, symptoms are present, or measurements are difficult to obtain, seek specialist input and follow local pathways.