Calculator of Alexandria

Target heart rate calculator (Karvonen)

Find your heart rate training zones from age and resting heart rate with the Karvonen method, and see where max heart rate formulas come from.

Count your pulse for a minute right after waking up.

Maximum heart rate from
Moderate zone, 70% (bpm)
Estimated maximum heart rate (bpm)
Heart rate reserve (bpm)

Formula

HRt=HRr+I (HRmax⁡−HRr)HR_t = HR_r + I\,(HR_{\max} - HR_r)
How it's derived

This calculator is for education. If you have a heart condition or take medication that affects heart rate, ask a doctor for your targets.

The formula

HRtarget=HRrest+I×(HRmax⁡−HRrest)HR_{\text{target}} = HR_{\text{rest}} + I \times (HR_{\max} - HR_{\text{rest}})

II is the intensity as a decimal (0.7 for 70%), HRrestHR_{\text{rest}} your resting heart rate and HRmax⁡HR_{\max} your maximum heart rate.

HRmax⁡=208−0.7×ageHR_{\max} = 208 - 0.7 \times \text{age}

Where it comes from

Heart rate reserve. In 1957 the Finnish physiologist Martti Karvonen noticed that percentages of maximum heart rate didn’t line up well with how hard exercise felt. His fix was to work only with the range your heart can actually add above rest, the heart rate reserve HRmax⁡−HRrestHR_{\max} - HR_{\text{rest}}. Training at 70% intensity means using 70% of that reserve, on top of your resting rate. Percentages of reserve turn out to track percentages of maximal oxygen uptake closely, which is the physiology that actually matters.

Maximum heart rate. The familiar 220−age220 - \text{age} appeared in the 1970s without a clear source. In 2001, Tanaka, Monahan and Seals pooled 351 studies covering 18,712 people and found 208−0.7×age208 - 0.7 \times \text{age} fitted much better, especially for older adults, where 220−age220 - \text{age} underestimates.

Worked example

Age 40, resting heart rate 65 bpm:

HRmax⁡=208−0.7×40=180 bpmHR_{\max} = 208 - 0.7 \times 40 = 180\ \text{bpm} HR70%=65+0.7×(180−65)=146 bpmHR_{70\%} = 65 + 0.7 \times (180 - 65) = 146\ \text{bpm}

Watch out for

  • Max heart rate varies a lot. Individuals differ by ±10 bpm or more from either formula. A supervised exercise test gives your real number.
  • Measure resting rate properly. Take it on waking, before getting up, over a few mornings.
  • Beta blockers and some other medications lower heart rate, which makes all these targets unreliable.

Sources

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