How to use this calculator
- Enter or choose maximum heart rate from.
- Enter or choose resting heart rate.
- Enter or choose exercise heart rate.
- The intensity (% of heart-rate reserve) updates as you type. Use Copy result or Share to keep it.
Method
HRR = HRmax − HRrest; %HRR = (HRexercise − HRrest) ÷ HRR × 100; HRmax (Tanaka) = 208 − 0.7 × age
- HRmax
- maximum heart rate, measured or estimated from age
- HRrest
- resting heart rate
- HRexercise
- heart rate during the activity
Worked example
- HRmax = 208 − 0.7 × 40 = 180 bpm.
- HRR = 180 − 60 = 120 bpm.
- %HRR = (132 − 60) ÷ 120 = 60%.
At 132 bpm, a 40-year-old with a resting heart rate of 60 is working at 60% of heart-rate reserve.
What the result means
%HRR tracks oxygen uptake more closely than %HRmax, which is why exercise guidelines often express intensity as a share of reserve. Use the Target Heart Rate Calculator to turn a chosen intensity into a heart-rate range.
Assumptions and limits
- Age-predicted maximum heart rate is a population average; an individual can differ by 10 bpm or more.
- Resting heart rate is measured at genuine rest.
- Beta-blockers and some other medicines lower heart rate and make these percentages misleading.
- Heat, dehydration and fatigue raise heart rate for the same effort.
Questions
What is the Karvonen method?
It sets exercise intensity as a percentage of heart-rate reserve and adds back the resting rate: target = rest + intensity × (max − rest).
Why does %HRR differ from %HRmax?
Because %HRmax starts from zero rather than from your resting rate, it always gives a higher figure for the same heartbeat.
Please note: This is a general screening estimate for adults, not medical advice or a diagnosis. Talk to a qualified health professional about your health.