Cardiac Risk (Framingham) Calculator

How it is calculated

The tool uses the 2008 Framingham general cardiovascular model (lipid version). It adds up sex-specific weights times the natural logarithms of age (years), total cholesterol, HDL and systolic blood pressure (cholesterol in mg/dL, pressure in mmHg), plus fixed amounts for smoking and diabetes. Then risk = 1 − S0exp(sum − mean), where S₀ and the mean are separate constants for men and women. The result is a 10-year percentage with one decimal, capped at 99%, with a plain-language line: "About 1 in N" below 50%, "About X in 10" from 50%, and "More than 9 in 10" from 95%. Under 10% is labelled low, 10 to under 20% intermediate, 20% and above high. Impossible inputs give no result: age outside 20 to 100, cholesterol outside 50 to 1000 or HDL outside 5 to 250, HDL above total cholesterol, or systolic pressure outside 50 to 300. The model comes from one population, so it can misestimate elsewhere. Treated blood pressure gets a larger weight.

Common mistakes

• Entering cholesterol in mmol/L (5.5 and 1.3). The model works in mg/dL, so these values are rejected and no result appears; multiply mmol/L by about 38.7 for total and HDL cholesterol first.
• Choosing "treated" for blood pressure when the person only had a single reading. The treated weight is larger, so risk rises (8.8% instead of 6.6% for a 55-year-old woman with 213, 50 and 130).
• Entering diastolic instead of systolic pressure. The model uses the top number, and a value such as 80 understates the risk.
• Swapping total cholesterol and HDL. HDL cannot exceed total cholesterol, so the swapped pair gives no result.
• Reading 11.8% as a prediction for one person. It is the average for people with the same inputs, and many other factors are not included.