ReckonBoxHow the target heart rate calculator works
A target heart rate is the beats-per-minute band you aim for while exercising. The American Heart Association puts moderate intensity near 50% to 70% of maximum heart rate and vigorous activity near 70% to 85%. Everything downstream depends on the maximum you start from, and that number is less settled than the charts suggest.
Enter your age and resting pulse and this tool computes zones from all three published equations, then shows the two competing zone methods side by side.
The formula the AHA uses is the weakest one available
Maximum heart rate is most commonly estimated as 220 minus your age, an equation published by Haskell and Fox in 1971. It's what the American Heart Association prints, and it underpins their chart for ages 20 to 70.
Two better-evidenced equations exist.
| Equation | Formula | Evidence base |
|---|---|---|
| Haskell and Fox (1971) | 220 - age | The long-standing rule of thumb |
| Tanaka, Monahan and Seals (2001) | 208 - 0.7 x age | 351 published studies, 18,712 individuals |
| Nes and colleagues, HUNT (2013) | 211 - 0.64 x age | 3,320 healthy adults aged 19 to 89 |
They agree closely around age 40 and separate at both ends of life, which is where the error does damage. NTNU's CERG, the group behind the HUNT Fitness Study, states that 220 minus age can underestimate maximum heart rate by as much as 40 beats per minute in seniors, and that the drift starts somewhere between ages 30 and 40.
For a 70 year old, Fox returns 150 bpm, Tanaka 159 and HUNT 166. Sixteen beats of disagreement, and the equation a cardiology charity publishes is the lowest of the three.
Worth noting who says what here. calculator.net, an ordinary calculator site, names all three equations with dates and states that maximum heart rate formulas have been criticised for outputting population averages, citing Olympic athletes whose measured maxima spanned 160 to 220 bpm. The medical bodies on this search mostly print one number and move on.
The finding nobody on this search carries: the error differs by sex
A 2018 cross-sectional study of 180 recreational marathon runners, 32 women and 148 men with a mean age of 43.2, compared both equations against measured maxima.
In men, Fox underestimated by 2.8 bpm while Tanaka showed no meaningful difference, making Tanaka the better fit. In women, both equations overestimated the measured maximum, Fox by 4.8 bpm and Tanaka by 4.9, with a large effect size. The authors recommend Tanaka for men with that training background and flag the overestimation in women explicitly.
Every calculator fetched for this build applies one age-only equation to everybody. If you're a woman, the numbers on this page and every other page may sit a few beats above your true figure.
Karvonen or plain percentage? They disagree, and it matters
The Karvonen method works from heart rate reserve: subtract resting heart rate from maximum, take a percentage of that reserve, then add the resting rate back. A plain percentage of maximum skips the reserve step entirely.
Take a 40 year old with a maximum of 180 and a resting pulse of 60. Reserve is 120. The bottom of the moderate band is 60 + (120 x 0.5), so 120 bpm by Karvonen. By the plain method it's 180 x 0.5, so 90 bpm.
Thirty beats apart, for the same person, on the same day.
The gap widens as resting heart rate rises, which means the fitter you are the more the two methods diverge. calculator.net shows the Karvonen equation; the AHA chart uses plain percentages. A reader checking both gets two different answers and no explanation of why, so this tool prints both and the gap between them.
What this page will not tell you
Which zone to train in. That's a coaching decision when you're well and a clinical one when you're not, and no calculator has the information to make it.
There's also no field test protocol here. NTNU CERG's own recommendation is individual testing over any calculator, because within-age variation is large, and that's fair. A maximal field test is something to arrange with a coach or clinician, not to attempt off the back of a web page.
The medication caveat is the one to take seriously. The AHA warns that some drugs lower both maximum heart rate and target zone, and advises anyone with a heart condition or on medication to ask a health care professional what their heart rate should be. Beta blockers in particular make every equation on this page inapplicable.
Results are estimates, not medical advice. For the effort side of a run, the pace calculator handles the speed and race prediction, and the calories burned calculator covers energy cost.
Frequently asked questions
What is a target heart rate? A target heart rate is the beats-per-minute band you aim for during exercise. The American Heart Association puts moderate intensity at about 50% to 70% of maximum heart rate and vigorous activity at about 70% to 85%. The band depends entirely on which maximum heart rate figure you start from.
Is 220 minus age accurate? It is the weakest of the three published equations, and it is the one the American Heart Association prints. NTNU CERG, which ran the HUNT Fitness Study, states that 220 minus age can underestimate maximum heart rate by as much as 40 beats per minute in seniors and starts drifting from ages 30 to 40. calculator.net notes that maximum heart rate formulas have been criticised for outputting population averages, citing Olympic athletes whose measured maxima spanned 160 to 220 bpm.
Which maximum heart rate formula should I use? The three come from very different evidence bases. Haskell and Fox (1971) gives 220 minus age. Tanaka, Monahan and Seals (2001) gives 208 minus 0.7 times age, drawn from 351 published studies covering 18,712 individuals. The HUNT equation (2013) gives 211 minus 0.64 times age from 3,320 adults aged 19 to 89. They agree near age 40 and separate at both ends of life.
Do these formulas work the same for women and men? No, and no calculator on this search says so. A 2018 study of 180 recreational marathon runners found that in women both the Fox and Tanaka equations overestimated measured maximum heart rate, by 4.8 and 4.9 beats per minute, with a large effect size. In men, Fox underestimated by 2.8 bpm while Tanaka showed no meaningful difference.
What is the Karvonen formula? Karvonen works from heart rate reserve: subtract your resting heart rate from your maximum, take a percentage of that reserve, then add the resting rate back. A 40 year old with a maximum of 180 and a resting rate of 60 has a reserve of 120, so 70% of the reserve is 84, and the target is 144 bpm.
Why do two calculators give me different zones for the same age? Because they use different methods and rarely say which. Karvonen accounts for resting heart rate; a plain percentage of maximum ignores it. For a 40 year old with a maximum of 180 and a resting rate of 60, the bottom of the moderate band is 120 bpm by Karvonen and 90 bpm by the plain method, a gap of 30 beats. The gap widens as resting heart rate rises.
Do medications affect these numbers? Yes. The American Heart Association warns that some drugs and medications lower both maximum heart rate and target zone, and advises anyone with a heart condition or on medication to ask a health care professional what their heart rate should be. These results are estimates, not medical advice.
Sources
- Nikolaidis et al., age-predicted maximal heart rate in recreational marathon runners (Fox and Tanaka accuracy by sex)
- NTNU CERG, the HUNT Fitness Study maximum heart rate calculator
- American Heart Association, target heart rates chart
- calculator.net target heart rate calculator, for the three named equations