ABI Calculator (Ankle-Brachial Index)

Created by Maria Kluziak and Aleksandra Zając, MD
Reviewed by Bogna Szyk and Jack Bowater
Based on research by
Stanford Medicine Measuring and Understanding the Ankle Brachial Index (ABI)
Last updated: Nov 28, 2022

This ABI calculator will help you calculate the results of an ankle-brachial index test. The ABI test is a quick, non-invasive procedure for diagnosing and preventing peripheral artery disease (PAD). Read on to learn more about its purpose, the results, and how to calculate ABI. While it's important to remember that this calculator is not equivalent to a proper medical checkup, you can use it if you're not sure if you should consult your doctor about your blood pressure and the risk of developing a cardiovascular disease in the future.

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. If any health condition bothers you, consult a physician.

How to use the ABI calculator?

To calculate your ankle-brachial index with our ABI calculator, please follow these steps:

  • Start by providing the ABI calculator with the highest systolic pressure taken in both arms.
  • The ankle-brachial index is calculated separately for each leg:
    • Input the highest blood pressure measured in your right leg to get your right ABI.
    • Input the highest blood pressure measured in your left leg to get your left ABI.

Measuring your blood pressure to calculate your ABI is a bit more complicated than a regular blood pressure checkup, so much so that it needs to be done by a doctor. They will walk you through it, and it's completely safe and noninvasive. However, if you're a smoker and you cannot stop smoking now, you need to refrain from smoking for at least 2 hours before the test to avoid the risk of cigarette-smoke-induced vasoconstriction of peripheral arteries occurring during the procedure, as it may alter the results.

How to interpret the ankle-brachial index?

NOTE: The information here is not equivalent to a medical checkup! This tool is meant to aid in assessing the risk of certain diseases. If you have any doubts or worries concerning your health, please consult your doctor.

Stanford Medicine provides the following guide to interpreting the ankle-brachial index values.

ABI

Interpretation

Recommended action

Above 1.4

Result indicates calcification or vessel hardening.

Consult a vascular specialist!

1.0 - 1.4

Normal

No action needed.

0.9 - 1.0

Acceptable

No action needed.

0.8 - 0.9

Mild arterial disease might be present.

Consult your doctor about the result and treat risk factors accordingly to their recommendations.

0.5 - 0.8

Moderate arterial disease.

Consult a vascular specialist!

Below 0.5

Severe arterial disease.

Consult a vascular specialist!

How to calculate ABI?

Your doctor definitely knows how to calculate ABI, but we understand that you might feel more confident if you also learn how to do it on your own. The formula used in the ABI calculator is very simple. It goes as follows:

Right ABI = highest right ankle systolic pressure / highest brachial systolic pressure

Left ABI = highest left ankle systolic pressure / highest brachial systolic pressure

  • Systolic blood pressure is the pressure on the walls of the blood vessels when the heart contracts. In a blood pressure reading, that's the first (and the higher) of the two values. For example, if your doctor tells you your blood pressure reading is 120 over 80, 120 is the systolic pressure.

  • Brachial refers to the brachial artery located in the upper arm.

When is ankle-brachial index calculated?

ABI is used to diagnose peripheral artery disease, a condition that causes the arteries to narrow, which in turn obstructs proper blood flow. This condition especially affects the legs, which is why doctors generally recommend doing an ABI test if you experience pain in your legs while walking, especially if PAD risk factors are present. These include diabetes, high blood pressure, high cholesterol, or a history of smoking.

Learn more about some of these diseases and complications by checking out our diabetes risk calculator and our cholesterol ratio calculator. If you need motivation to quit smoking, you may find some of that through our quit smoking calculator. Stay healthy!

Maria Kluziak and Aleksandra Zając, MD
To calculate ABI, measure the blood pressure in both arms, and use the higher of the two numbers for both leg calculations.

Please start by providing the highest pressure measured in the arms.
Highest pressure in both arms
mmHg
ABI for the right leg
Highest pressure in right foot
mmHg
ABI
ABI for the left leg
Highest pressure in left foot
mmHg
ABI
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