ABI Calculator — Ankle-Brachial Index
Calculate the Ankle-Brachial Index (ABI), the standard non-invasive screening ratio for peripheral arterial disease (PAD). Enter the ankle and brachial systolic blood pressures measured with a Doppler probe to get the ABI and its clinical interpretation.
mmHg
mmHg
ABI = ankle systolic pressure ÷ brachial systolic pressure
- 1
Ankle systolic pressure
130 mmHg - 2
Brachial systolic pressure
125 mmHg - 3
Ankle-Brachial Index (ABI)
130 ÷ 125 = 1.04Normal range 1.0–1.4; below 0.9 suggests peripheral arterial disease.
此計算機如何運作？
ABI = ankle systolic pressure ÷ brachial systolic pressure. A result of 1.0–1.4 is normal; below 0.9 indicates peripheral arterial disease (PAD); above 1.4 suggests non-compressible arteries (arterial calcification). ABI is measured clinically with a Doppler probe and must be interpreted by a healthcare professional.
公式
How this is calculated
The Ankle-Brachial Index compares blood pressure at the ankle with blood pressure at the arm. In a healthy vascular system, the ankle systolic pressure should be equal to or slightly higher than the brachial pressure, giving an ABI of 1.0–1.4. Narrowing of the arteries (stenosis) due to atherosclerosis reduces flow to the legs, lowering the ankle pressure relative to the arm and producing an ABI below 1.0.
Clinically, ABI is measured by inflating a blood-pressure cuff at the ankle and arm, then using a Doppler probe to detect the return of blood-flow signal as the cuff deflates. For each limb, the highest of the dorsalis pedis and posterior tibial pressures is used as the ankle reading; the higher of the two brachial pressures is used as the denominator. This calculator uses those two numbers to compute the ratio.
The AHA/ACC interpretation thresholds (used in this calculator) are: > 1.4 non-compressible (arterial calcification, common in diabetes, may give a falsely elevated reading); 1.0–1.4 normal; 0.9–1.0 borderline; 0.7–0.89 mild PAD; 0.4–0.69 moderate PAD; < 0.4 severe PAD. This tool is for educational reference only — clinical decisions must be made by a healthcare professional.
常見問題
An ABI below 0.9 is the standard diagnostic threshold for PAD. Values of 0.7–0.89 suggest mild PAD (often asymptomatic or causing leg pain with exercise), 0.4–0.69 suggest moderate PAD (may cause rest pain), and below 0.4 indicates severe or critical limb ischaemia requiring urgent vascular evaluation.
An ABI greater than 1.4 suggests that the ankle arteries are stiff and non-compressible — typically due to medial calcification, which is common in people with diabetes, chronic kidney disease or advanced age. In this case the ABI is falsely elevated and does not accurately reflect flow restriction. A toe-brachial index (TBI) is often used instead.
No. ABI must be measured with a hand-held Doppler probe and a calibrated pressure cuff — the numbers you enter here should come from a clinical measurement. This calculator interprets the ratio according to published thresholds for educational awareness only. Any result suggesting PAD should be confirmed and managed by a vascular specialist.
也稱為
TG we-Calculate Editorial Team. (2026). ABI Calculator — Ankle-Brachial Index [Online calculator]. TG we-Calculate. https://we-calculate.com/zh-tw/calculator/abi-calculator
TG we-Calculate Editorial Team. "ABI Calculator — Ankle-Brachial Index." TG we-Calculate. 2026. https://we-calculate.com/zh-tw/calculator/abi-calculator.
TG we-Calculate Editorial Team, "ABI Calculator — Ankle-Brachial Index," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/zh-tw/calculator/abi-calculator
@misc{wecalculate_abi_calculator, title = {ABI Calculator — Ankle-Brachial Index}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/zh-tw/calculator/abi-calculator}}, year = {2026}, note = {TG we-Calculate} }
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