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Cardio calculator

Karvonen formula calculator

Get your target heart rate from heart-rate reserve — the Karvonen method, which uses your resting heart rate as well as your max. Free, instant, no sign-up.

TARGET HEART RATE
147bpm
Heart-rate reserve 124 bpm — 184 max minus 60 resting
Max heart rate estimated as 208 − 0.7 × age = 184 bpm

Your Karvonen zones

Zone 1
Recovery — very light
50–60% HRR
122–134 bpm
Zone 2
Easy — aerobic base
60–70% HRR
134–147 bpm
Zone 3
Aerobic — tempo
70–80% HRR
147–159 bpm
Zone 4
Threshold — hard
80–90% HRR
159–172 bpm
Zone 5
Maximum — VO2/anaerobic
90–100% HRR
172–184 bpm

Knowing the number is step one — the coach decides how many minutes a week you spend there.

What is the Karvonen formula?

The Karvonen formula sets training heart rates from your heart-rate reserve — the beats between resting and maximum — instead of from maximum alone. Published by Karvonen, Kentala and Mustala in 1957, it is the method most coaching bodies use when a resting heart rate is available.

How this calculator works

Target heart rate = ((max HR − resting HR) × intensity) + resting HR. With a max of 180 and a resting rate of 70, the reserve is 110 beats, so 60% intensity lands at (110 × 0.60) + 70 = 136 bpm. If you don't know your max we estimate it as 208 − 0.7 × age (Tanaka).

Karvonen vs percent of max

Percent-of-max zones ignore your resting heart rate, so a fit runner with a resting rate of 45 and an untrained one at 75 get the same easy zone even though their reserves differ by 30 beats. Karvonen fixes that, which is why the two methods disagree most at low intensities — exactly where most of your training sits.