Estimate your max heart rate
The same Tanaka fallback the app uses. It truncates instead of rounding, so it agrees with Zonas to the beat. Enter a measured maximum if you have one.
Max heart rate is individual. An age formula is a low-friction starting point, not a measurement — a measured or coach-prescribed maximum is always better when you have one.
This calculator exists for one narrow reason:
It should return the same fallback max heart rate that Zonas uses.
Formula
HRmax = 208 - trunc(0.7 x age)The calculator does not round.
That matters most when 0.7 x age has a decimal part:
| Age | Calculation | Result |
|---|---|---|
| 25 | 208 - trunc(17.5) | 191 |
| 30 | 208 - trunc(21.0) | 187 |
| 40 | 208 - trunc(28.0) | 180 |
If another calculator gives 190 for age 25, it is probably rounding. Zonas truncates.
Why This Is Only A Fallback
Maximum heart rate is individual.
Age formulas are useful because they are low friction. They are not precise enough to settle every training decision.
If you have a measured max heart rate, use it.
If you do not, the Tanaka estimate is a reasonable starting point for automatic zones.
How Zonas Uses HRmax
Zonas uses max heart rate to calculate:
- percent-HRmax zones when resting heart rate is missing
- Karvonen heart rate reserve zones when resting heart rate exists
- weekly moderate/vigorous cutpoints in the app
- custom boundary BPM values
It is a shared input.
That is why the calculator needs to match the app exactly.
What This Tool Does Not Do
It does not detect your real maximum.
It does not know your medications, heat exposure, training status, sleep, caffeine, illness, or whether a high workout reading was clean.
It returns the Zonas fallback. Nothing more.
Common questions
What formula does this max heart rate calculator use?
It uses Tanaka: 208 minus trunc(0.7 times age), matching the current Zonas app.
Why does the calculator truncate?
The iOS app uses Swift Int conversion. The web calculator mirrors that behavior so the calculator and app agree.
Is estimated max heart rate accurate?
It is an estimate. Use a measured or coach-prescribed max heart rate if you have one.
Sources
- Age-predicted maximal heart rate revisited
Primary source for the Tanaka 208 - 0.7 x age estimate.
- Target Heart Rates Chart
Public target heart rate guidance commonly uses age-predicted maximum heart rate as a starting point.