Health
Target Heart Rate Calculator
The three formulas agree at middle age and pull apart at the edges. This page shows the spread, and treats the target zone as a band rather than a line.
How the three formulas drift apart with age
They cluster around 40 and separate toward both ends. Read down the spread: the older the age, the more 220 − age underestimates, and the wider the gap the choice of formula opens.
| Age | Maximum heart rate (average of three) | Spread across the three formulas |
|---|---|---|
| 20 yearsFox reads highest here — 220 − 20 = 200. | 197 | 6 |
| 30 years | 190 | 5 |
| 40 yearsThe default above. The three land within 5 beats. | 182 | 5 |
| 55 years | 170 | 11 |
| 70 yearsA spread of 16 beats, and 220 − age now reads lowest of the three. | 158 | 16 |
The formula
Worked example
A 40-year-old
- Fox: 220 − 40 = 180; Tanaka: 208 − 0.7 × 40 = 180; Nes: 211 − 0.64 × 40 = 185
- here the three nearly agree — a coincidence of this age — a spread of 5
- average 182, so the moderate zone is 64% to 76% of it
- 116 to 138 bpm
Where this goes wrong
Trusting 220 − age, or reading the zone as a precise line
220 − age is the formula everyone knows and the one to trust least. At 40 the three happen to land within 5 beats — 180, 180 and 185 — but that agreement is a coincidence of middle age. At 20, Fox reads highest of the three; at 70 it reads lowest, and they spread about 16 beats. On top of that, even the best-fitted formula, Tanaka, carries a standard deviation of roughly 10 beats between individuals, so a real maximum can sit most of a zone-width away from any estimate. Read the target zone as a broad band, cross-check it against how you actually feel — at a moderate effort you should be able to talk but not sing — and if you have a heart condition or take medication that affects heart rate, take these numbers to a clinician rather than acting on them alone.
Questions
- Is 220 minus age accurate?
- Not very. It was never derived as a precise formula, and it systematically reads high for younger people and low for older ones. Tanaka’s 208 − 0.7 × age fits the data better across the age range. But no age-based formula is exact: individual maximum heart rates vary by about ten beats either way, so any of these is a starting estimate, not a measurement.
- How do I find my actual maximum heart rate?
- The only accurate way is a supervised graded exercise test, where intensity is raised in stages until your heart rate plateaus. Field estimates from a hard effort — the peak of an all-out hill repeat, say — get closer than a formula, but a formula is the safe starting point. Anyone with a heart condition should only test maximum effort under medical supervision.
- What is the moderate-intensity zone?
- The American Heart Association puts moderate-intensity exercise at 64% to 76% of maximum heart rate. This page reads that band off the average of the three formulas. Because the maximum itself is uncertain, treat the zone as a guide and pair it with the talk test: at a moderate effort you can hold a conversation but not sing.
- Why does the calculator not use the Karvonen method?
- The Karvonen method folds in your resting heart rate to give a zone off your heart rate reserve, which is a refinement — but it rests on the same uncertain maximum, so it inherits the same spread. This page keeps the focus on that spread. If you know your resting heart rate, the Karvonen zone will sit a little higher than the plain-percentage one shown here.