This ABI calculator helps you quickly determine your ankle-brachial index—a simple but powerful screening tool for peripheral artery disease. Whether you're checking results after a clinic visit or you're a clinician running a quick calculation between patients, this tool gives you instant ABI values with clear interpretation for both legs.

Here's what the test actually measures: it compares blood pressure at your ankle to blood pressure in your arm. Healthy arteries maintain similar pressure throughout your body, so a significant drop between your arm and ankle can signal reduced blood flow in your legs—one of the earliest warning signs of PAD.

The good news? PAD is highly treatable when caught early. Understanding your ABI puts you one step ahead.

Think of ABI as a simple ratio: ankle pressure divided by arm pressure. That's it. But this straightforward calculation tells us something remarkably useful about your circulation.

In a healthy vascular system, blood pressure at your ankle runs equal to or slightly higher than pressure in your arm. When plaque builds up in your leg arteries (a process called atherosclerosis), less blood reaches your ankles. Lower blood flow means lower pressure readings—and that's exactly what ABI detects.

What makes this test so valuable is its accuracy. With sensitivity around 90% and specificity of 98%, ABI catches significant arterial disease better than almost any other non-invasive screening tool available.

But here's something many people don't realize: ABI isn't just about your legs. Research consistently shows that people with low ABI have higher rates of heart attack and stroke—even when they have zero leg symptoms. Your ankle pressure is actually a window into your overall cardiovascular health.

Your ABI falls into one of these categories:

Normal (1.00-1.40): Your leg arteries are doing their job. Keep doing what you're doing—maintain those heart-healthy habits.

Borderline (0.91-0.99): You're in a gray zone, and honestly, this is where interpretation gets tricky. You don't have PAD by strict definition, but you're close enough that it's worth paying attention. Focus on the things you can control: quit smoking if you smoke, keep your blood pressure and cholesterol in check, stay active. Your doctor will probably want to recheck in 6-12 months.

Mild to Moderate PAD (0.40-0.90): Blood flow to your legs is genuinely reduced. Many people at this stage feel completely fine—no pain, no symptoms—which is exactly why screening matters. The disease can progress silently. Treatment usually involves medication, a structured walking program (surprisingly effective), and getting serious about risk factors.

Severe PAD (Below 0.40): This needs attention now. Blood flow is critically low, and you're at risk for rest pain, wounds that won't heal, and in worst cases, tissue loss. A vascular specialist should evaluate you promptly to discuss your options.

Step 1: Enter Your Highest Arm Blood Pressure Put in the highest systolic (top number) reading from either arm, measured in mmHg. Tested both arms? Use whichever was higher—this prevents underestimating any disease.

Step 2: Enter Your Right Foot Pressure Input the systolic pressure measured at your right ankle. In clinical settings, this is taken using a blood pressure cuff and Doppler probe at the dorsalis pedis or posterior tibial artery.

Step 3: Enter Your Left Foot Pressure Same thing for the left side.

Step 4: Check Your Results The calculator instantly shows your ABI for each leg with an interpretation. We calculate each leg separately because PAD doesn't always affect both sides equally—more on that below.

The math couldn't be simpler:

ABI = Ankle Systolic Pressure ÷ Arm Systolic Pressure

Each leg gets its own calculation using the same arm pressure as the denominator.

Say your measurements come back as:

• Highest arm pressure: 130 mmHg
• Right ankle pressure: 124 mmHg
• Left ankle pressure: 91 mmHg

Right leg: 124 ÷ 130 = 0.95 → Borderline Left leg: 91 ÷ 130 = 0.70 → Mild PAD

See the difference? Your right leg looks pretty good—just slightly below the normal cutoff. But your left leg is telling a different story. That kind of asymmetry matters clinically and would definitely warrant a closer look at what's happening on the left side.

First, don't worry if your numbers aren't identical. Small differences of 0.05-0.10 between legs are completely normal—bodies aren't perfectly symmetrical.

Larger gaps, though? Those are worth understanding.

What's actually happening when one side is lower:

Atherosclerosis doesn't follow rules about fairness. Plaque can build up heavily in your left iliac artery while your right side stays relatively clear. It's the same disease process, just hitting one leg harder than the other.

Previous injuries, blood clots, or surgeries can also create lasting differences in circulation between legs. And some people simply have anatomical variations that produce slight pressure differences—nothing pathological, just how they're built.

The practical takeaway:

If your right leg shows a healthy 1.05 while your left comes back at 0.78, that left-sided number is what matters for your risk profile. Your doctor will focus diagnostic attention there. And here's a useful rule of thumb: a difference greater than 0.15 between legs—even if both technically fall in the "normal" range—is worth mentioning to your healthcare provider. It can signal early or localized disease before the numbers look obviously abnormal.

ABI works beautifully for most people. But certain conditions can throw off the results, and knowing about these limitations helps you interpret your numbers correctly.

This is the big one. If you have diabetes, chronic kidney disease, or you're older, calcium can deposit in your artery walls over time. Calcified arteries become stiff—almost pipe-like—and they don't compress normally when the blood pressure cuff inflates.

The result? Falsely high ABI readings, often above 1.40. Your actual circulation might be compromised, but the numbers look reassuringly normal or even elevated.

This isn't a test failure. It's a known limitation, and there are workarounds:

Toe-brachial index (TBI): The tiny arteries in your toes almost never calcify. A TBI below 0.70 suggests PAD even when standard ABI looks fine. This is the go-to alternative for diabetic patients.

Pulse volume recordings: Measures how blood volume in your legs changes with each heartbeat—calcification doesn't affect it.

Duplex ultrasound: Directly visualizes blood flowing through your arteries. You can see the narrowing rather than inferring it from pressure differences.

Just exercised? Blood pressure shifts after physical activity. Sit quietly for 10-15 minutes before testing.

Had coffee or a cigarette recently? Both affect vascular tone. Skip them for at least 2 hours pre-test if you want accurate numbers.

Feeling anxious? Stress elevates blood pressure readings. Take some slow breaths. The test itself is painless—just cuffs inflating.

PAD, heart disease, and stroke all share the same root cause: atherosclerosis, the gradual accumulation of fatty deposits in artery walls. Knowing your risk factors puts you in control.

Smoking — This is the big one. Smokers are 2-6 times more likely to develop PAD compared to non-smokers. If you take away one thing from this page: quitting smoking is the single most effective step you can take. Nothing else comes close.

Diabetes — High blood sugar damages artery walls and speeds up plaque formation. People with diabetes have 2-4 times the PAD risk. Keeping your glucose well-controlled genuinely makes a difference.

High blood pressure — Years of elevated pressure wear down your artery linings. Managing blood pressure protects both your heart and your legs.

High cholesterol — LDL cholesterol is literally the raw material for plaque. Statins don't just lower your numbers—they stabilize existing plaque and slow disease progression.

Age — Risk climbs after 50 and rises further after 65. You can't change your birthday, but you can control the other factors.

• Family history of heart disease, stroke, or PAD
• Chronic kidney disease
• Obesity and physical inactivity
• History of cardiovascular events

Stack multiple risk factors together and screening becomes especially important. Catching PAD early—before symptoms develop—gives you the most options.

An abnormal result is important information, not a crisis. Here's what actually happens at each stage:

Your doctor may recommend:

• Getting serious about modifiable risk factors—especially smoking cessation, blood pressure, and cholesterol
• Starting a walking program (structured exercise genuinely improves circulation)
• Rechecking ABI in 6-12 months to see if things are stable or progressing

No procedures. No panic. Just smart monitoring.

Now we're into territory where more evaluation makes sense:

Duplex ultrasound — A painless scan that shows blood flowing through your arteries in real time. It pinpoints where blockages are and how severe they've become.

Medication adjustments — If you're not already on antiplatelet therapy (aspirin or clopidogrel) and a statin, you probably will be. These drugs reduce cardiovascular events in PAD patients.

Supervised exercise therapy — This sounds too simple to work, but the data is compelling. Structured walking programs improve pain-free walking distance by 50-200% in many patients. It's essentially physical therapy for your arteries.

Vascular specialist referral — If symptoms are bothersome or disease is progressing despite conservative measures.

At this level, you need vascular expertise promptly:

Angiography — Detailed imaging showing exactly where and how badly your arteries are blocked.

Revascularization discussion — Depending on the pattern of disease, options might include angioplasty (balloon and stent) or bypass surgery. The right choice depends on anatomy, symptoms, and your overall health.

An abnormal ABI doesn't mean surgery is inevitable. Plenty of people manage PAD for years with lifestyle changes and medication alone. Early detection is the whole point—it gives you time and options that you wouldn't have if the disease announced itself with a crisis.

This calculator provides estimates for educational purposes. ABI results should always be interpreted by a qualified healthcare provider who knows your complete medical history. An abnormal result is a reason to have a conversation with your doctor—not to diagnose or treat yourself.