HesapHanem

Heart Rate Reserve Calculator

Enter your age and resting heart rate to find your heart rate reserve.

How it is calculated

The tool estimates your maximum heart rate with the simple age formula HRmax = 220 − age, then subtracts your resting pulse: HRR = HRmax − HRrest. If you also enter an intensity percentage it applies the Karvonen formula: target = HRR × (intensity ÷ 100) + HRrest. Age is in years, resting pulse and every result in beats per minute (bpm), rounded to a whole number. Age and resting pulse must both be above zero; the intensity field is optional, and without it you only get HRmax and HRR. The 220 − age rule is a population average, so a real maximum can easily differ by 10 beats or more either way.

Worked example

Take a 40-year-old with a resting pulse of 60 bpm who wants to train at 70% intensity. HRmax = 220 − 40 = 180 bpm. HRR = 180 − 60 = 120 bpm. Target = 120 × 0.70 + 60 = 84 + 60 = 144 bpm. The tool shows a maximum of 180 bpm, a reserve of 120 bpm and a target of 144 bpm.

Try this example →

Common mistakes

  • Entering the resting pulse measured after getting out of bed and walking around, or after coffee. Count it lying down, just after waking, otherwise the reserve is too small and every target is too high.
  • Typing the intensity as a fraction such as 0.7. The field expects a percentage, so 0.7 means 0.7% and gives a target barely above your resting pulse.
  • Entering an intensity above 100. The tool does not stop you: 110% on the example gives 192 bpm, which is above the estimated maximum.
  • Treating the target as exact. It rests on 220 − age, which is only an average; a trained or older person may have a very different true maximum.
  • Expecting the target to equal a plain percentage of HRmax. Karvonen adds the resting pulse back, so 70% of HRR (144 bpm here) is higher than 70% of HRmax (126 bpm).

Sources

About this calculator

Heart rate reserve (HRR) is the gap between maximum and resting heart rate: HRR = HRmax − HRresting. The Karvonen method uses HRR to set exercise intensity more accurately than percentage-of-max alone: target HR = (HRR × intensity%) + HRresting, which accounts for individual fitness by anchoring the range to each person's actual resting pulse.

Personal trainers and coaches use Karvonen-based target heart rate zones to prescribe specific effort levels (e.g., 60-70% for fat-burning, 80-90% for high-intensity intervals), and cardiac rehabilitation programs use it to keep patients exercising safely within a doctor-approved intensity range.

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Comments (1)

  • Editorial team

    Sanity-check the output: the target should always sit between your resting pulse and the estimated maximum, and it rises faster than you might expect as intensity climbs. The 220 minus age maximum is only an average, and some medicines, beta blockers among them, lower heart rate, so if you take medication or have a heart condition, ask your doctor for your own zones. How do you measure your resting pulse?

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