ABPI Calculator (Ankle Brachial Pressure Index Tool)

Use this tool to calculate the Ankle Brachial Pressure Index (ABPI) for both legs. Enter systolic pressures below to assess for Peripheral Arterial Disease (PAD) according to UK clinical standards.

Values saved automatically to device

1 Brachial Systolic (Arms)

2 Ankle Systolic (Legs)

Right Leg

Left Leg

How to use this ABPI Calculator

To use this ABPI Calculator, enter the systolic pressure readings from both arms and each ankle. The tool then calculates the right and left ankle brachial pressure index and shows a simple interpretation range to help you understand whether the result is normal, borderline, low, or unusually high.

Interpretation Guide (UK Standard)

ABPI Range
Clinical Interpretation
> 1.40
High / Non-compressible
1.00 – 1.40
Normal
0.91 – 0.99
Borderline
0.70 – 0.90
Mild PAD
0.40 – 0.69
Moderate PAD
< 0.40
Severe PAD
Compression Therapy & Wound Care Context

IMPORTANT: This information is for general educational purposes only. Always follow local NHS Trust guidelines and NICE recommendations.

  • ABPI 0.8 – 1.3: Generally considered safe for standard high-compression therapy (e.g., 4-layer bandage) in the absence of other contraindications.
  • ABPI 0.5 – 0.8: Often indicates mixed aetiology. Reduced compression (modified) may be considered under specialist supervision.
  • ABPI < 0.5: Compression is usually contraindicated due to risk of arterial occlusion and tissue necrosis. Urgent vascular assessment required.
  • ABPI > 1.3: Compression should be applied with caution as vessel calcification may mask true arterial pressure. TBI recommended.

Understanding ABPI

The Ankle Brachial Pressure Index (ABPI) is a vital assessment tool used across the NHS and private practice to detect peripheral arterial disease (PAD). By comparing the systolic blood pressure at the ankle (using the dorsalis pedis or posterior tibial arteries) to the brachial artery pressure in the arm, clinicians can objectively assess leg circulation.

Correct measurement requires a Doppler ultrasound probe to detect the return of blood flow as the sphygmomanometer cuff is deflated. This calculator assists in the immediate computation of the index, reducing manual errors and providing instant interpretation based on standard clinical ranges.

Frequently Asked Questions

What is ABPI/ABI?
The Ankle Brachial Pressure Index (ABPI), also known as Ankle-Brachial Index (ABI), is a non-invasive test used to assess the circulation in your legs. It compares the blood pressure in your ankle to the blood pressure in your arm. It is the primary tool used in the UK by clinicians, nurses, and podiatrists to screen for Peripheral Arterial Disease (PAD).
How do you calculate ABPI for each leg?
ABPI is calculated by taking the highest systolic pressure measured at the ankle for that leg and dividing it by the highest systolic brachial (arm) pressure measured from either arm.
Which arm pressure should I use?
You should measure systolic pressure in both arms. The calculation always uses the highest reading of the two arms as the denominator (baseline), assuming flow to the arms is normal.
Which ankle artery reading should I use (DP vs PT)?
In a full assessment, you measure both the Dorsalis Pedis (DP) and Posterior Tibial (PT) arteries. The standard calculation uses the higher of the two values for the numerator. This tool\'s \'Simple Mode\' assumes you are entering the highest obtained value, while \'Advanced Mode\' lets you input both.
What is a normal ABPI?
A normal resting ABPI is typically between 1.00 and 1.30 (some guidelines suggest up to 1.40). This indicates adequate blood supply to the limb.
What does ABPI below 0.9 mean?
An ABPI of 0.90 or less is generally considered diagnostic of Peripheral Arterial Disease (PAD). Values between 0.70–0.90 suggest mild PAD, 0.40–0.69 suggest moderate PAD, and below 0.40 indicates severe PAD (critical limb ischaemia).
What does ABPI above 1.4 mean?
An ABPI > 1.40 often indicates calcified, non-compressible arteries (arterial stiffness), common in patients with diabetes or chronic kidney disease. This renders the result unreliable, and alternative tests like the Toe-Brachial Index (TBI) may be required.
Can diabetes affect ABPI results?
Yes. Diabetes can cause calcification of the medial arterial wall, making blood vessels difficult to compress. This can lead to falsely high ABPI readings.
ABPI vs Toe-Brachial Index (TBI)
If ABPI is high (>1.4) or unreliable due to calcification, a TBI is often performed. Toe vessels are less susceptible to calcification.
Why might ABPI be repeated?
If there is a significant difference between arms (>10mmHg) or results are borderline, repeating the test after a period of rest or on a different day helps confirm accuracy.
Is this tool a diagnosis?
No. This calculator is a clinical aid and informational tool. It does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional.
When should I speak to my GP/clinician?
If you have symptoms of leg pain when walking (claudication), non-healing wounds, or if your ABPI result is abnormal, seek clinical advice.
How is the test performed (Doppler)?
The test requires a hand-held Doppler ultrasound probe and a blood pressure cuff. The cuff is inflated until the pulse signal stops, then slowly deflated to detect the pressure at which flow returns (systolic pressure).
Any prep tips before measurement?
The patient should rest supine (lying flat) for at least 10 minutes prior to measurement to stabilise blood pressure. Avoid caffeine or smoking immediately before the test.

Tool intended for clinical guidance only. Not for diagnostic use.