Ankle-Brachial Index Calculator
Calculate your ABI to assess the risk of peripheral artery disease (PAD) by comparing blood pressure in your ankles and arms.
Important Health Disclaimer
This calculator provides general health information based on standard medical formulas and WHO guidelines. Results are for informational and educational purposes only and should not be considered as professional medical advice or a personal care recommendation.
For health concerns, medical conditions, fitness plans, or dietary decisions, please consult with qualified healthcare professionals, licensed physicians, registered dietitians, or certified fitness trainers who can evaluate your individual health status and medical history.
Individual health needs vary significantly. These calculations are general estimates and may not be appropriate for everyone, especially those with existing medical conditions, pregnant women, children, or elderly individuals.
Not a substitute for qualified professional guidance
Blood Pressure Readings
Enter systolic (top number) blood pressure readings in mmHg
Arm Pressures
Ankle Pressures
Lowest ABI (Left Leg)
1.07
Normal
Interpretation
Normal ankle-brachial index. Continue healthy habits.
Risk Level: Low
ABI Reference Ranges
What Is the Ankle-Brachial Index (ABI)?
The Ankle-Brachial Index (ABI) is a simple, non-invasive test that compares the blood pressure in your ankles to the blood pressure in your arms to screen for Peripheral Artery Disease (PAD) — a condition where narrowed arteries reduce blood flow to the limbs. ABI is calculated by dividing the highest ankle systolic blood pressure by the highest arm systolic blood pressure. A normal ABI ranges from 1.0 to 1.3, indicating that blood pressure at the ankle is equal to or slightly higher than at the arm.
PAD affects approximately 8-12 million Americans and becomes increasingly common with age, diabetes, and smoking. The condition often goes undiagnosed because many patients are asymptomatic or attribute leg pain to aging. ABI screening is recommended for all adults over 65 and for younger individuals with risk factors including diabetes, smoking, hypertension, and hyperlipidemia. The test takes only a few minutes using a blood pressure cuff and a handheld Doppler ultrasound device.
An ABI below 0.90 is diagnostic for PAD with approximately 95% sensitivity and 99% specificity when compared to angiography. Values below 0.40 indicate severe, limb-threatening disease. Conversely, ABI values above 1.30 suggest arterial calcification (often seen in diabetes and chronic kidney disease) where vessels become incompressible, and the test loses accuracy — these patients require alternative testing such as toe-brachial index or arterial duplex ultrasound.
How ABI Is Calculated
The ABI calculation uses the highest systolic pressure from each limb:
Ankle-Brachial Index Formula
Where:
- Highest Ankle Systolic= The higher systolic reading between the right and left ankle (dorsalis pedis or posterior tibial artery), in mmHg
- Highest Arm Systolic= The higher systolic reading between the right and left brachial artery, in mmHg
ABI Interpretation Categories
| ABI Value | Category | Clinical Significance |
|---|---|---|
| Below 0.40 | Severe PAD | Critical limb ischemia risk. Urgent vascular referral required. Rest pain or tissue loss may be present. |
| 0.40 – 0.69 | Moderate PAD | Significant arterial obstruction. Vascular specialist consultation recommended. Claudication symptoms likely. |
| 0.70 – 0.89 | Mild PAD | Early arterial disease. Lifestyle modification, risk factor control, and monitoring indicated. |
| 0.90 – 0.99 | Borderline | Not diagnostic but warrants close follow-up, especially with risk factors or symptoms. |
| 1.00 – 1.30 | Normal | No significant arterial obstruction. Continue cardiovascular risk management. |
| Above 1.30 | Incompressible | Arterial calcification (common in diabetes, CKD). Alternative testing (toe-brachial index) needed. |
How to Use This ABI Calculator
- Enter Arm Systolic Pressures: Input the systolic (top number) blood pressure from both the right and left arms, measured at the brachial artery. The higher of the two values is used as the denominator.
- Enter Ankle Systolic Pressures: Input the systolic pressure from both the right and left ankles, measured at either the dorsalis pedis or posterior tibial artery using a Doppler device. The higher of the two ankle readings is used as the numerator.
- Review Individual and Overall ABI: The calculator computes ABI for each leg individually and identifies the lower (worse) value with its corresponding risk category.
Important: Accurate ABI measurement requires a handheld Doppler ultrasound and properly sized blood pressure cuffs. This calculator interprets measurements obtained by a healthcare professional — it does not replace clinical measurement or diagnostic testing.
Worked Examples
Normal ABI
Problem:
Right arm: 130 mmHg, Left arm: 126 mmHg, Right ankle: 140 mmHg, Left ankle: 138 mmHg. Calculate ABI.
Solution Steps:
- 1Highest arm: max(130, 126) = 130 mmHg
- 2Highest ankle: max(140, 138) = 140 mmHg
- 3ABI = 140 / 130 = 1.08
- 4Right leg ABI: 140/130 = 1.08; Left leg ABI: 138/130 = 1.06
Result:
Overall ABI = 1.08 (Normal). Both legs show normal ankle-brachial indices, indicating adequate arterial perfusion to the lower extremities. No evidence of peripheral artery disease.
Moderate PAD — Left Leg
Problem:
Right arm: 140 mmHg, Left arm: 135 mmHg, Right ankle: 145 mmHg, Left ankle: 82 mmHg.
Solution Steps:
- 1Highest arm: 140 mmHg
- 2Right ABI: 145/140 = 1.04 (Normal)
- 3Left ABI: 82/140 = 0.59 (Moderate PAD)
Result:
Right leg ABI = 1.04 (Normal), Left leg ABI = 0.59 (Moderate PAD). The significant asymmetry between legs indicates unilateral peripheral artery disease, most likely in the left iliac or femoral arteries. This patient should be referred to a vascular specialist.
Tips & Best Practices
- ✓ABI should be measured after 5-10 minutes of rest in a supine position for accurate results
- ✓A difference of more than 0.15 between the right and left ABI is clinically significant — it suggests unilateral disease
- ✓Exercise ABI (measuring before and after treadmill walking) can unmask PAD in patients with normal resting ABI but exertional symptoms
Frequently Asked Questions
Sources & References
Last updated: 2026-06-06
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Sources
- •World Health Organization (WHO) — Global health metrics, disease classification, and nutritional standards. who.int
- •Centers for Disease Control and Prevention (CDC) — Health statistics, BMI guidelines, and disease prevention data. cdc.gov
- •National Institutes of Health (NIH) — Medical research, clinical guidelines, and health calculators. nih.gov
- •Mayo Clinic — Clinical health information, disease reference, and wellness guidance. mayoclinic.org
For a complete list of all references used across the site, visit our full sources page.
Editorial Note
MyCalcBuddy Editorial Team
This page is maintained as an educational calculator reference.
Formula Source: WHO Health Metrics Standards
by World Health Organization