Age

Resting heart rate (bpm)

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General estimate for planning only — not medical advice. Consult a doctor about your specific situation.

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Zone heart rate targets climbing from recovery to max effort — Zones span 123 to 185 bpm for a 35-year-old.

Method & verification

How This Tool Works

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Calculation Method

Max HR = 220 - Age

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BoringToolsKit methodology and verification standard

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Assumptions to Verify

These tools provide general estimates for planning and education only.
They are not medical advice and not a substitute for a qualified healthcare professional.
Always consult your doctor or another healthcare provider about your specific situation.

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A worked example: age 35, resting 60 bpm

Take a 35-year-old with a resting heart rate of 60 bpm. Max HR is 220 minus 35, which gives 185 bpm. The Karvonen formula then works on the spread between max and rest: 185 minus 60 leaves 125 beats as the trainable range, and each zone percentage is applied to that range before the resting rate is added back.

Zone 1 at 50 percent is 125 times 0.5, or 62.5, plus 60, which rounds to 123 bpm; at 60 percent it is 75 plus 60, or 135 bpm. Zone 2 tops out at 70 percent: 87.5 plus 60 rounds to 148 bpm. Zone 3 runs from 148 to 160 bpm (125 times 0.8 is 100, plus 60). Zone 4 spans 160 to 173 bpm, and Zone 5 reaches the full 185 bpm at 100 percent.

Notice what resting HR does here. The same 35-year-old with a resting rate of 50 instead of 60 would see Zone 2 shift from 135 to 149 bpm at the top end. A fitter heart squeezes the zone targets upward, which is exactly why the resting input is not optional decoration.

Where the numbers break down

The 220 minus age estimate carries a standard error of roughly 10 to 12 bpm. For a 45-year-old, predicted max HR is 175, but the true value could plausibly sit anywhere from about 160 to 190. That spread is larger than the entire width of one zone, so a training session near a zone boundary may genuinely belong to the neighbour.

Two edge cases are worth naming. First, very high resting rates distort the maths: a resting rate of 90 with age 30 gives a trainable range of only 100 beats, and Zone 1 bottom lands at 140 bpm, a number that feels like hard work rather than recovery. Illness, stress, caffeine, and poor sleep can all push resting HR up 5 to 10 bpm overnight, so measure it on waking over several days and average.

Second, beta blockers suppress heart rate by 10 to 20 bpm or more, making every zone here unsafe to use without clinical guidance. If your measured max HR from a hard, honest effort differs from the estimate by more than about 8 bpm, rebuild your zones around the measured figure instead.