Ankle Brachial Index Calculator
Calculate the Ankle Brachial Index (ABI) to assess peripheral artery disease by comparing blood pressure in your ankle and arm.
How to Use This Calculator
- Enter the highest systolic blood pressure reading from the brachial artery (arm)
- Enter the highest systolic blood pressure reading from the ankle
- Select which leg was measured (right or left)
- Click Calculate to see your ABI result and interpretation
Formula Used
ABI = Ankle Systolic Blood Pressure ÷ Brachial Systolic Blood Pressure
Where:
- ABI = Ankle Brachial Index (dimensionless ratio)
- Ankle Systolic Blood Pressure = Highest systolic pressure reading from the posterior tibial or dorsalis pedis artery (mmHg)
- Brachial Systolic Blood Pressure = Highest systolic pressure reading from the brachial artery (mmHg)
Example Calculation
Real-World Scenario:
A 65-year-old patient with diabetes undergoes ABI testing to screen for peripheral artery disease.
Given:
- Brachial Systolic Blood Pressure = 130 mmHg
- Ankle Systolic Blood Pressure = 104 mmHg
- Leg Measured = Right
Calculation:
ABI = 104 ÷ 130 = 0.80
Result: ABI of 0.80, which indicates mild peripheral artery disease.
Why This Calculation Matters
Practical Applications
- Screening for peripheral artery disease (PAD)
- Assessing cardiovascular risk
- Monitoring disease progression or treatment effectiveness
Key Benefits
- Non-invasive and inexpensive screening tool
- Helps identify asymptomatic patients with PAD
- Provides prognostic information for cardiovascular events
Common Mistakes & Tips
Frequently Asked Questions
Borderline: 0.91-0.99
Mild PAD: 0.71-0.90
Moderate PAD: 0.41-0.70
Severe PAD: ≤0.40
Non-compressible arteries: >1.4
References & Disclaimer
Medical Disclaimer
This calculator is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
References
- 2016 AHA/ACC Guideline on the Management of Patients With Lower Extremity Peripheral Artery Disease - American Heart Association/American College of Cardiology guideline with recommendations on ABI testing
- Ankle-Brachial Index - National Center for Biotechnology Information overview of ABI methodology and interpretation
- How Is Peripheral Artery Disease Diagnosed? - National Heart, Lung, and Blood Institute information on diagnostic tests including ABI
Accuracy Notice
ABI calculations are most accurate when performed by trained healthcare professionals using appropriate equipment. Factors such as calcified arteries (common in diabetes) can produce falsely elevated ABI values. This calculator provides an estimate but should not replace clinical evaluation.
About the Author
Kumaravel Madhavan
Web developer and data researcher creating accurate, easy-to-use calculators across health, finance, education, and construction and more. Works with subject-matter experts to ensure formulas meet trusted standards like WHO, NIH, and ISO.