Bruce Protocol METs Calculator

A MET is a unit that estimates the energy your body uses during physical activity. One MET equals approximately 3.5 ml of oxygen per kilogram of body weight per minute — the amount consumed at rest. An activity with a MET of 5 means you're burning about 5 times the energy you would sitting still.

The Bruce Protocol is a standardized, graded treadmill exercise test used to evaluate cardiovascular fitness and detect heart conditions. It consists of incremental stages (typically up to 7), each lasting 3 minutes, where both the speed and incline of the treadmill increase progressively. The total time you sustain the test is used to estimate your aerobic capacity.

For males, METs are calculated as: METs = (14.8 − 1.379T + 0.451T² − 0.012T³) / 3.5, where T is total test time in minutes (including fractional seconds). For females, the formula is: METs = (4.38T − 3.9) / 3.5. VO₂ max is then estimated as METs × 3.5.

Generally, a score above 10 METs is considered good cardiovascular fitness for most adults. For individuals aged 40–49, scores of 9–10 METs are average; above 11 METs is excellent. For those over 60, scores above 8 METs are considered good. Below 5 METs is associated with higher cardiac risk regardless of age.

Stage 4 of the Bruce Protocol begins at 12 cumulative minutes of testing. Using the male formula, completing exactly 12 minutes yields approximately 12.1 METs. For females using the linear formula, 12 minutes corresponds to roughly 11.1 METs. The exact value depends on how many seconds into stage 4 the test was stopped.

The 85% MPHR is a commonly used target heart rate during stress testing. It is calculated as 85% of the estimated maximum heart rate, which is often derived from the formula (220 − age). Reaching 85% MPHR is generally considered an adequate level of cardiac stress for a diagnostic exercise test.

VO₂ max reflects how efficiently your heart and lungs deliver oxygen to working muscles — a key indicator of cardiovascular health. Higher VO₂ max values are associated with lower risk of heart disease, metabolic syndrome, and all-cause mortality. It is one of the strongest predictors of long-term health outcomes.

The test is stopped when the patient reaches their target heart rate, experiences chest pain, severe shortness of breath, dizziness, significant ST-segment changes on ECG, a drop in blood pressure, or requests to stop. The duration at termination is the value used to calculate METs and VO₂ max.