Abi Index Calculator > Interpretation > Chart

Our vital abi index calculator helps determine the ratio between systolic blood pressure in the ankle and arm using ABI = P_ankle / P_arm formula.

• ABI 1.0 – 1.4: Normal. This suggests that blood flow in the legs is normal.
• ABI 0.9 – 1.0: Borderline or mild peripheral artery disease (PAD).
• ABI 0.5 – 0.9: Moderate PAD. Further testing and treatment may be required.
• ABI < 0.5: Severe PAD. Urgent medical intervention is needed.
• ABI > 1.4: Abnormally high ABI may indicate non-compressible arteries due to calcification, commonly seen in diabetes and older age. Further tests are recommended.

Abi Index Calculator

Arm Pressure (mmHg)	Ankle Pressure (mmHg)	ABI	Interpretation
130	135	1.04	Normal
140	112	0.80	Mild to moderate PAD
125	160	1.28	Normal (upper limit)
135	68	0.50	Moderate PAD
120	180	1.50	Calcified arteries
110	95	0.86	Mild PAD
145	130	0.90	Acceptable
150	100	0.67	Moderate PAD
128	132	1.03	Normal
115	90	0.78	Mild PAD
140	150	1.07	Normal
125	70	0.56	Severe PAD
130	125	0.96	Acceptable
138	142	0.97	Acceptable
90	105	1.17	Normal

ABI Index Interpretation Chart

ABI Value	Interpretation
<0.5	Severe arterial disease
0.5 – 0.8	Moderate arterial disease
0.8 – 0.9	Mild arterial disease might be present
0.9 – 1.0	Acceptable
1.0 – 1.4	Normal range
>1.4	Calcification of vessels
1.5 – 1.9	Significant calcification
>2.0	Extreme calcification
1.2 – 1.4	High normal
0.91 – 0.99	Borderline PAD

ABI Index Formula

The ABI is calculated using the following formula:

ABI = (Highest ankle systolic pressure) / (Highest arm systolic pressure)

Suppose we have the following measurements:

• Right arm systolic pressure: 130 mmHg
• Left arm systolic pressure: 128 mmHg
• Right ankle systolic pressure: 120 mmHg
• Left ankle systolic pressure: 118 mmHg

To calculate the ABI:

Identify the highest arm pressure: 130 mmHg (right arm)

Identify the highest ankle pressure: 120 mmHg (right ankle)

Apply the formula: ABI = 120 / 130 = 0.92

This result indicates borderline PAD and warrants further investigation.

How to Calculate Ankle-Brachial Index?

Calculating the ABI involves several steps:

• Measure systolic blood pressure in both arms
• Measure systolic blood pressure in both ankles (dorsalis pedis and posterior tibial arteries)
• Identify the highest pressure for each limb
• Divide the highest ankle pressure by the highest arm pressure

Example……..

• Right arm: 125 mmHg
• Left arm: 128 mmHg
• Right ankle (dorsalis pedis): 115 mmHg
• Right ankle (posterior tibial): 118 mmHg
• Left ankle (dorsalis pedis): 120 mmHg
• Left ankle (posterior tibial): 122 mmHg

Calculation:

Highest arm pressure: 128 mmHg
Highest ankle pressure: 122 mmHg
ABI = 122 / 128 = 0.95

What is ABI Index Pressure?

ABI index pressure refers to the comparative blood pressure measurements used in calculating the ABI. It involves assessing systolic pressures in both the upper and lower extremities to determine circulatory efficiency.

Consider these measurements:

• Brachial pressure: 140 mmHg
• Ankle pressure: 130 mmHg

The ABI index pressure ratio would be:

ABI = 130 / 140 = 0.93

This value suggests borderline PAD, prompting further evaluation.

What Does an ABI of 1.5 Mean?

An ABI of 1.5 is above the normal range and may indicate calcified arteries. This condition, often seen in patients with diabetes or chronic kidney disease, can lead to artificially high ankle pressures.

If a patient’s arm pressure is 120 mmHg and their ankle pressure reads 180 mmHg:

ABI = 180 / 120 = 1.5

This elevated ABI suggests arterial stiffness, which can mask underlying PAD and requires additional diagnostic methods like toe-brachial index or duplex ultrasound.

References

• National Heart, Lung, and Blood Institute. “Peripheral Artery Disease.” https://www.nhlbi.nih.gov/health-topics/peripheral-artery-disease
• Mayo Clinic. “Ankle-brachial index.” https://www.mayoclinic.org/tests-procedures/ankle-brachial-index/about/pac-20392934

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