Example data table
| Left Brachial | Right Brachial | Left DP | Left PT | Right DP | Right PT |
|---|---|---|---|---|---|
| 132 | 128 | 118 | 122 | 110 | 114 |
Formula used
ABI is computed for each leg as: ABI = (selected ankle systolic pressure) ÷ (selected brachial systolic pressure). This tool can use the highest ankle artery, the average ankle arteries, and either the highest or lowest arm value.
How to use this calculator
- Measure systolic brachial pressures in both arms.
- Measure ankle systolic pressure at DP and PT arteries.
- Select your preferred method for numerator and denominator.
- Enter values in mmHg, then calculate ABI.
- Review left, right, and overall interpretation bands.
- Use exports to save results for documentation.
FAQs
1) What does ABI measure?
ABI compares ankle systolic pressure to arm systolic pressure. Lower ratios suggest reduced blood flow to the legs and possible peripheral artery disease.
2) Which ankle pressure should I use?
Many protocols use the higher of dorsalis pedis and posterior tibial for each ankle. Some settings use the average instead; choose the method that matches your workflow.
3) Why use the highest arm pressure?
Using the higher brachial pressure helps reduce false low ABI values when one arm has arterial narrowing. Some protocols use the lower arm to screen asymmetry.
4) What ABI range is considered normal?
Often 1.00 to 1.40 is considered normal. Values 0.91 to 0.99 may be borderline, while 0.90 or lower can indicate peripheral artery disease.
5) What does ABI above 1.40 mean?
Values above 1.40 can reflect noncompressible, calcified vessels, especially in diabetes or kidney disease. Toe-brachial index or imaging may be considered clinically.
6) Can ABI be used after exercise?
Yes. Post-exercise ABI can reveal flow limitations not seen at rest. Use the same leg and arm measurement technique and document timing after activity.
7) How accurate is ABI?
Accuracy depends on proper cuff size, patient position, rest time, and measurement technique. Repeat readings if values seem inconsistent or symptoms do not match results.
8) Is this calculator a medical diagnosis?
No. It provides educational calculations and interpretation bands. Diagnosis and treatment decisions should be made by qualified clinicians using full clinical context.