Ankle-Brachial Index Calculator

The Ankle-Brachial Index (ABI) is a simple, non-invasive test used to screen for peripheral artery disease (PAD) — a condition where arteries in the legs become narrowed or blocked due to plaque buildup. It is one of the most reliable early indicators of cardiovascular disease.

How ABI is Calculated

The formula is straightforward:

ABI = Ankle Systolic Pressure ÷ Arm (Brachial) Systolic Pressure

You measure the systolic blood pressure (the top number) at the ankle and at the upper arm (brachial artery). Then divide the ankle reading by the arm reading. The result is a ratio — a pure number with no units.

Interpreting Your ABI Score

• Above 1.40 — Arteries may be stiff or calcified (common in diabetics). Requires further evaluation.
• 1.00 – 1.40 — Normal. Arteries are open and flowing well.
• 0.91 – 0.99 — Borderline. Mild narrowing may be present. Monitor closely.
• 0.71 – 0.90 — Mild PAD. Some restriction in blood flow to the legs.
• 0.41 – 0.70 — Moderate PAD. Significant narrowing. Medical review recommended.
• 0.40 or below — Severe PAD. High risk for leg tissue damage and cardiovascular events.

Who Should Check Their ABI?

ABI screening is recommended for anyone over 50 with risk factors such as smoking, diabetes, high blood pressure, high cholesterol, or a family history of heart disease. People with leg pain while walking (claudication) should also be tested.

Practical Example

If your ankle systolic pressure is 120 mmHg and your brachial pressure is 130 mmHg: ABI = 120 ÷ 130 = 0.92

This falls in the borderline range, suggesting a follow-up with your doctor is wise.

Important Note

ABI is a screening tool, not a diagnosis. Always discuss your result with a healthcare provider. This calculator is for educational purposes only.