Heart Rate Zones
7 calculators
Heart rate calculators work from an estimated maximum, then divide the range below it into zones. Both halves of that carry error, and the first half carries most of it.
The tools here cover the competing maximum-heart-rate equations, the two common ways of defining zones, and the recovery figure taken in the minute after an effort stops.
- Heart Rate Zones (% of Max) Calculate five heart-rate training zones from age-based maximum heart rate using the Fox formula.
- Heart Rate Zones (Karvonen Method) Calculate target heart rate zones using the Karvonen heart rate reserve method.
- Max Heart Rate Calculator (220 Minus Age) Estimate maximum heart rate using the classic 220-minus-age formula.
- Max Heart Rate Calculator (Tanaka Formula) Estimate maximum heart rate using the Tanaka age-prediction equation (208 - 0.7 × age).
- Max Heart Rate Comparison Calculator (4 Formulas) Compare Fox, Tanaka, Gulati, and Nes max heart rate predictions side-by-side.
- Target Heart Rate Calculator Calculate target heart rate zones from maximum heart rate and exercise intensity.
- Heart Rate Recovery Calculator Calculate the drop in heart rate during the first minute after exercise stops.
The maximum heart rate estimates disagree with each other
The familiar 220 − age formula has no published derivation behind it; it entered circulation in the 1970s as a convenience and was never validated as a measurement. Its standard deviation against measured maxima is commonly reported at around 10 to 12 beats per minute, which at a given age covers a range of roughly 40 beats.
Tanaka (208 − 0.7 × age) came from a meta-analysis of 351 studies and fits observed data better across the adult age range, particularly for older adults where 220 − age tends to underestimate. Gulati (206 − 0.88 × age) was derived specifically in women, in whom the older formulas were fitted mostly on men. Nes (211 − 0.64 × age) came from a large Norwegian cohort.
Running the same age through all four shows the spread directly. At 40 years old they return figures between 171 and 180 bpm, and every zone boundary derived from them inherits that nine-beat difference.
Percent-max zones and Karvonen zones are not the same scale
Percent-of-maximum zones take a straight fraction of the maximum figure. The Karvonen method works instead from heart rate reserve — the span between resting and maximum heart rate — and adds the resting rate back afterwards. For the same nominal percentage the two return different absolute heart rates, and Karvonen returns the higher one.
The gap widens as resting heart rate falls, which means the two methods diverge most for the trained people most likely to be using them. A zone quoted as "70%" is ambiguous until the method behind it is stated.
Because both are built on an estimated maximum, an error in that estimate propagates into every zone. A measured maximum from a maximal test removes the largest single source of error in the chain.
Common questions
Is 220 minus age accurate?
It is a rough approximation with no original research behind it, and its error is large: studies report a standard deviation of roughly 10 to 12 beats per minute against measured maxima. That means a substantial share of people of any given age sit more than ten beats away from what it predicts. Tanaka and Nes were derived from actual datasets and fit observed data better, particularly for adults over about 40, where 220 − age tends to read low.
What is the difference between percent-max and Karvonen zones?
Percent-max takes a fraction of maximum heart rate directly. Karvonen works from heart rate reserve — maximum minus resting — takes the fraction of that span, then adds the resting rate back. For the same stated percentage Karvonen returns a higher absolute heart rate, and the two diverge further as resting heart rate drops. A zone percentage is therefore not portable between the two methods without recalculating.
Should I use an estimated or a measured maximum heart rate?
A measured maximum removes the largest error in the chain, because every zone boundary is a percentage of that one figure. Estimating formulas carry a standard deviation of around ten beats, which propagates into every zone derived from them. Where a measured figure from a maximal effort is available, the zone calculators accept it directly in place of an estimate.