ABI Calculator
Enter the highest systolic pressure recorded from either arm (mmHg)
Highest systolic pressure at the right ankle (mmHg)
Highest systolic pressure at the left ankle (mmHg)
Risk Factor Checklist
Select any that apply — used to provide personalized context
Enter Your Blood Pressure Values
Input brachial and ankle blood pressures to calculate your Ankle-Brachial Index and assess peripheral artery disease risk.
Glossary
Doppler Ultrasound
A non-invasive imaging technique that uses sound waves to measure blood flow velocity and detect arterial stenosis. Used clinically to record systolic pressures at each measurement site during ABI testing.
Dorsalis Pedis (DP)
The dorsalis pedis artery runs along the top of the foot and is one of two arteries used to measure ankle systolic pressure during ABI testing.
Posterior Tibial (PT)
The posterior tibial artery runs behind the inner ankle bone (medial malleolus) and is the second ankle artery used in ABI measurement. The highest reading from DP and PT is used.
Toe-Brachial Index (TBI)
An alternative to ABI for patients with calcified arteries. Measured using a small cuff on the great toe. Normal TBI is above 0.70. Preferred in diabetic and chronic kidney disease populations.
Medical Disclaimer
This calculator is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for interpretation of ABI values and any medical decisions. ABI measurement accuracy depends on proper technique; results entered manually may differ from clinically measured values.
How to Use This ABI Calculator
Choose Simple or Advanced Mode
Select Simple Mode if you have a single brachial (arm) pressure reading and one reading per ankle — this covers most clinical and screening scenarios. Select Advanced Mode if you have separate readings for the right and left arms, and separate dorsalis pedis (DP) and posterior tibial (PT) readings for each ankle. Advanced mode mirrors the full clinical protocol and automatically selects the highest value from each measurement group.
Enter Blood Pressure Readings in mmHg
Enter all systolic blood pressure values in millimetres of mercury (mmHg). In Simple Mode: enter the highest brachial (arm) pressure from either arm, the right ankle pressure, and the left ankle pressure. In Advanced Mode: enter right arm, left arm, right DP, right PT, left DP, and left PT pressures. All values must be positive numbers greater than zero. Leave a field blank if a reading was unobtainable.
Review ABI Values and Clinical Interpretation
The calculator computes a separate ABI for each leg to two decimal places and maps each result to one of six clinical categories: Non-Compressible, Normal, Borderline, Mild PAD, Moderate PAD, or Severe PAD. Read the interpretation text and recommended next steps for each leg. The severity gauge shows both legs' positions on the ABI scale simultaneously, and an inter-leg difference flag will appear if asymmetry exceeds 0.15.
Use the Report and Checklist for Next Steps
Complete the risk factor checklist to receive personalized context about whether ABI screening is especially important for you. Add optional patient information (name, date, clinician) and click Print Report to generate a printable clinical summary. Use the CSV export to save your readings for follow-up tracking. Share the printed or saved results with your healthcare provider at your next appointment.
Frequently Asked Questions
What is a normal ABI value?
A normal ABI falls between 1.00 and 1.40. This range indicates that the systolic blood pressure at the ankle is at least as high as the arm pressure, which is expected in healthy arteries because the lower limb vasculature amplifies pressure slightly. Values in this range are generally associated with no significant peripheral artery disease. Most major vascular societies, including the American Heart Association and the European Society of Cardiology, use 0.90 as the diagnostic threshold: an ABI below 0.90 is considered abnormal and indicates PAD of varying severity. Values above 1.40 are also abnormal but for a different reason — they suggest arterial calcification rather than stenosis.
What does an ABI below 0.90 mean?
An ABI below 0.90 indicates peripheral artery disease (PAD), meaning there is significant narrowing of the arteries supplying blood to the legs. The lower the value, the more severe the disease. Values from 0.71 to 0.90 suggest mild PAD, often causing calf pain during walking (claudication) that resolves with rest. Values from 0.41 to 0.70 suggest moderate PAD with greater functional impairment. Values at or below 0.40 suggest severe PAD or critical limb ischemia, which can threaten limb viability and requires urgent specialist evaluation. Importantly, ABI below 0.90 is also an independent cardiovascular risk marker associated with increased rates of heart attack and stroke, even in patients with no leg symptoms.
Why is ABI above 1.40 a problem?
An ABI above 1.40 is considered non-compressible and is not a sign of good circulation — rather, it indicates that the arteries are calcified and too stiff to compress with a blood pressure cuff. This makes the measured systolic pressure artificially high, so the ABI ratio is overestimated. This pattern is most common in people with diabetes mellitus, chronic kidney disease, and advanced age. When ABI exceeds 1.40, it cannot be used to rule out PAD. The recommended alternative is the Toe-Brachial Index (TBI), which uses a specialized small cuff placed on the great toe. Toe arteries calcify much less frequently, so TBI remains reliable in most calcification cases. A normal TBI is generally above 0.70.
How does the inter-leg ABI difference matter?
A difference in ABI between the right and left legs can indicate unilateral (one-sided) arterial disease. A difference of up to 0.10–0.15 can occur due to measurement variability and is considered normal. However, when the inter-leg difference exceeds 0.15, clinicians consider this clinically significant asymmetry. It suggests that one leg may have greater arterial obstruction than the other, which can guide imaging decisions — for example, duplex ultrasound of the more affected leg. Our calculator automatically computes the absolute difference between your right and left ABI values and flags it when it crosses this threshold, alerting you to discuss the finding with your provider.
Who should be screened with an ABI test?
Major cardiology and vascular guidelines recommend ABI screening for all adults aged 70 and over, regardless of symptoms. Screening is also recommended for adults aged 50–69 who have a history of smoking or diabetes. Additionally, ABI testing is indicated for any patient who has exertional leg pain (especially calf pain that stops with rest), non-healing foot or leg wounds, or absent or diminished peripheral pulses on physical examination. In wound-care settings, ABI is used before applying compression bandaging — an ABI above 0.80 is generally required for safe full compression therapy. Patients with known coronary artery disease or stroke may also benefit, as PAD and cardiovascular disease frequently co-exist.
What is the accuracy of the ABI test?
The ABI has approximately 90% sensitivity and 98% specificity for detecting significant PAD compared to digital subtraction angiography, which is the reference standard. This means ABI correctly identifies about 90 of every 100 people who truly have significant PAD, and correctly identifies 98 of every 100 people who do not have significant PAD. The high specificity makes it a reliable tool for ruling in disease. However, the 10% false-negative rate means some patients with PAD — particularly those with borderline values of 0.91–0.99 — may need exercise ABI testing or imaging to confirm or exclude the diagnosis. Measurement technique is important: values should be obtained with the patient supine and at rest for at least five minutes before the first reading.