Target Heart Rate Calculator

Most heart rate calculators hand you five zones and leave you to work out which one today’s session belongs in. This one asks that question first. Tell it what you are training for and it returns a single range to aim at, how long to hold it, and what it should feel like.

If you want the full five-zone table instead, that is the heart rate zones calculator, which also accepts a max heart rate you have actually measured. If you specifically want to see how far the Karvonen method differs from plain percentage-of-max for you, the Karvonen calculator puts the two side by side.

How the number is worked out

Everything starts from an estimated maximum heart rate:

Tanaka: MHR = 208 − (0.7 × Age)

The familiar 220 − Age came out of a 1971 literature review rather than an experiment, and it drifts in opposite directions at the two ends of the age range. Tanaka fits measured data better, so it is the default here, and the result shows what the other one would have given.

Give a resting heart rate as well and the calculator switches to Karvonen, which works off your heart rate reserve rather than your maximum:

HRR = MHR − Resting HR Target = (HRR × intensity) + Resting HR

The difference is not cosmetic. A 30-year-old with a resting pulse of 65 gets 150 to 163 bpm for aerobic work from Karvonen, and 131 to 150 bpm from plain percentage-of-max. That is 19 bpm at the bottom of the range, wide enough to put you in the wrong session entirely. Percentage-of-max behaves as though your resting rate were zero, so it under-prescribes hardest for the fittest people, which is a strange way for a training tool to fail.

What each goal maps to

About the fat burning zone

It is real and it is widely misunderstood. At low intensity a larger proportion of the energy you burn comes from fat, which is where the name comes from. But the total is smaller. Half an hour at 65% burns fewer calories than half an hour at 80%, and body fat responds to the total, not the ratio. The reason the low band is still the right answer for most people trying to lose weight is duration: you can do an hour at that intensity several times a week and recover from it, which you cannot do at threshold. Pick the intensity you will actually repeat.

On accuracy

Any age-based maximum carries about ±10 to 15 bpm of individual variation, which is wider than the gap between the two formulas people argue about. If a range feels obviously wrong, believe your body. Wrist optical sensors also lag 10 to 15 seconds into an interval and can lock onto your cadence instead of your pulse; a chest strap is worth the money if you train by heart rate at all. Check with a doctor before starting anything new, particularly if you are on a beta blocker, which lowers both resting and maximum heart rate and makes every number on this page an underestimate of your effort.