Free Ankle-Brachial Index (ABI) Calculator
Quickly calculate and interpret bilateral lower-extremity arterial ratios using standard systolic blood pressure readings. Designed with evidence-based clinical formulas and clear visual scale meters.
Interactive ABI Assessment
Enter the resting systolic blood pressure in mmHg for both arms and both ankles. Results calculate dynamically as you type.
Awaiting Blood Pressure Inputs
Enter valid systolic blood pressure readings (40–300 mmHg) for both arms and ankles above, or click to see a live calculation.
Left Leg ABI
Right Leg ABI
Standard ABI Educational Reference Classification
| ABI Range | Classification | General Interpretation | Recommended Medical Action |
|---|---|---|---|
| 1.00 – 1.40 | Normal range | Adequate lower-extremity arterial blood perfusion. | Routine preventive cardiovascular health maintenance. |
| 0.91 – 0.99 | Borderline | Equivocal perfusion; may indicate early or mild flow impedance. | Discuss with doctor; consider post-exercise treadmill testing. |
| 0.41 – 0.90 | Possible reduced blood flow | Associated with mild to moderate arterial obstruction or claudication. | Schedule a medical consultation for vascular evaluation. |
| 0.00 – 0.40 | Severely reduced range | May indicate critical limb ischemia or severe arterial blockage. | Prompt medical evaluation and urgent vascular specialist review. |
| > 1.40 | Non-compressible arteries | Stiff or calcified vessel walls prevent normal cuff occlusion. | Physician evaluation; alternative tests like Toe-Brachial Index (TBI). |
* Based on American Heart Association (AHA) and Society for Vascular Surgery (SVS) clinical practice guidelines for the assessment of peripheral arterial disease.
How to Use This Calculator
A straightforward guide to entering blood pressure values and understanding standard clinical calculation methodology.
Measure Both Arms
Measure or obtain resting systolic blood pressure from both the left and right arms in mmHg.
Enter Arm Readings
Input both values into the calculator. The system automatically detects and selects the higher value.
Enter Ankle Values
Enter the highest systolic pressure obtained at each ankle (dorsalis pedis or posterior tibial).
Automatic Ratio
The calculator divides each leg's ankle pressure by the highest arm pressure independently.
Review with Doctor
Review your bilateral results and discuss any questions or risk factors with your healthcare provider.
Watch: How an ABI Test Is Performed
An authoritative clinical teaching demonstration illustrating cuff placement, Doppler probe positioning, and acoustic signal interpretation.
Ankle Brachial Index (ABI) Test: How to Perform
Demonstration of Doppler probe positioning, brachial occlusion, and ankle systolic measurement.
Privacy-enhanced playback via youtube-nocookie.com (deferred on demand)Frequently Asked Questions
Clear, evidence-grounded answers to common questions about ankle-brachial index testing.
What is an ankle-brachial index?
The ankle-brachial index (ABI) is an objective non-invasive vascular test comparing the systolic blood pressure measured at the ankle with the systolic blood pressure measured in the upper arm (brachial artery). It provides clinical insight into arterial circulation reaching the lower extremities.
How is ABI calculated?
ABI is calculated by dividing the systolic blood pressure at the ankle by the highest systolic blood pressure measured between both arms. The formula is: Leg ABI = Ankle Systolic Pressure ÷ Highest Arm Systolic Pressure.
Why is the higher arm pressure used?
Using the higher arm systolic reading provides the most reliable estimate of central systemic arterial perfusion pressure. If one subclavian or brachial artery has mild stenosis, the lower arm reading would underestimate systemic pressure and falsely inflate the calculated ankle ratio.
What is considered a normal ABI range?
An ABI between 1.00 and 1.40 is widely considered the normal reference range, suggesting adequate arterial blood flow to the lower extremity under resting conditions.
Can this calculator diagnose peripheral artery disease?
No. This online calculator is strictly an educational tool. A medical diagnosis of peripheral artery disease (PAD) requires an in-person clinical assessment by a licensed healthcare provider, standard continuous-wave Doppler probe examination, waveform analysis, and comprehensive cardiovascular history.
What does an ABI above 1.40 mean?
An ABI greater than 1.40 generally indicates non-compressible, calcified, or stiffened arterial walls (often referred to as medial arterial calcification or Mönckeberg's arteriosclerosis). It is commonly seen in patients with long-standing diabetes or chronic kidney disease and usually warrants alternative diagnostic evaluations, such as a toe-brachial index (TBI).
When should I talk to a healthcare professional?
You should speak with a qualified physician or vascular specialist if you experience leg pain while walking (claudication), unexplained numbness, persistent coldness in one foot, non-healing sores or ulcers on your feet or toes, or if your readings consistently fall outside the normal 1.00 to 1.40 range.
Is this calculator storing my blood pressure readings?
No. This tool does not store, transmit, log, or share any blood pressure numbers or calculated results. All mathematical evaluations run 100% locally in your device's web browser, maintaining total privacy.
About Ankle-Brachial & Contact
Our Mission: The Ankle-Brachial Index Calculator is an independent, non-commercial educational resource developed to help patients, caregivers, and medical learners understand the mechanics and clinical interpretation of the ankle-brachial index test.
Strict Privacy Commitment: This site does not collect, record, or transmit health data or personal blood pressure entries. All calculations occur strictly within your web browser. No trackers, health profiles, or analytics cookies are used.
Contact Information: For inquiries, feedback, or general educational correspondence, please reach out via:
* Please note that we cannot provide individualized medical advice, clinical diagnoses, or review private patient records. For personal health concerns, consult a licensed healthcare professional.