Heart Rate Calculator

The Karvonen formula calculates target heart rate using your heart rate reserve (HRR), which is the difference between your maximum and resting heart rate. The formula is: THR = (HRR × desired intensity%) + resting HR. This method is considered more personalised than simply using a percentage of maximum heart rate alone.

Measure your resting heart rate (HR rest) first thing in the morning before you get out of bed. Count your pulse for 60 seconds, or count for 15 seconds and multiply by 4. The average adult resting heart rate is between 60–100 bpm, with well-trained athletes often below 60 bpm.

The Gellish formula (206.9 − 0.67 × age) is generally considered more accurate across a wider range of ages, especially for older adults. The simpler 220 − age formula tends to overestimate HRmax in younger people and underestimate it in older individuals. If you have had a maximal exercise test, entering your actual HRmax is always the most precise option.

Heart rate reserve is the difference between your maximum heart rate and your resting heart rate (HRR = HRmax − HRrest). It represents the range over which your heart can increase its rate during exercise. A larger HRR is generally associated with better cardiovascular fitness.

Very Light (<19% HRR) is gentle recovery activity. Light (20–39%) improves basic endurance. Moderate (40–59%) builds aerobic fitness and is ideal for general health. Hard (60–84%) improves cardiovascular performance and is typical of structured training. Very Hard (≥85%) is high-intensity effort used for peak performance training and should be approached cautiously.

RPE stands for Rating of Perceived Exertion, commonly using the Borg 6–20 scale. It is a subjective measure of how hard exercise feels. Each heart rate training zone corresponds to an RPE range — for example, Moderate intensity corresponds roughly to an RPE of 10–11 on the Borg scale. RPE is useful when a heart rate monitor isn't available.

HRR-based ranges (Karvonen) account for individual fitness level by incorporating resting heart rate, making them more personalised. HRmax-based percentages are simpler but less individualised. For general population use both are valid; for athletes or those with specific fitness goals, the HRR method is generally preferred by exercise physiologists.

This calculator provides general exercise guidance based on established formulas, but it is not a substitute for medical advice. If you have a known heart condition, have been sedentary, or are starting a new exercise programme, consult your doctor or a cardiac rehabilitation specialist before using heart rate zone training.