Karvonen Heart Rate Zones Calculator

Target HR = ((max HR − resting HR) × intensity) + resting HR. The HRR (heart rate reserve) method.

Inputs

If unknown, use max-hr-by-age first.

Result

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How to use this calculator

  • Measure true resting HR (lying in bed before getting up).
  • Estimate or test max HR.
  • Read the zone you want to train in.
  • Heart rate strap > optical for accuracy.

About this calculator

The Karvonen formula uses heart rate reserve (HRR = max HR − resting HR) instead of just max HR. This better accounts for fitness level — a fitter person with lower resting HR gets larger HRR and slightly different zones than the simple %-of-max method. A 40-year-old with rest 60 and max 185: HRR = 125. Z2 (aerobic base) is then 60% × 125 + 60 = 135 bpm to 70% × 125 + 60 = 147 bpm. Lower than the naive 60-70% of max (111-130).

Frequently asked

Why Karvonen vs. % of max?+
% of max under-counts effort at low intensities — a dead-still resting "0% effort" still has a HR. Karvonen anchors to your reserve, which is more honest.
How do I find true resting HR?+
Lie in bed motionless for 5 min before getting up. Use a chest strap or pulse-check at the wrist. Optical watches at rest read ±5 bpm.
Are 5 zones standard?+
Yes for most coaches. Some elite programs use 7 zones (Coggan/Friel). The 5-zone model is universal for general fitness.
What if I don't know my max HR?+
Use max-hr-by-age. The Tanaka formula (208 − 0.7 × age) is more accurate than the old 220 − age, especially over 40.
Does Karvonen apply to cycling and running equally?+
Yes — heart rate reflects systemic effort regardless of mode. Cycling HR tends to read 5-10 bpm lower than running at same effort due to muscle pump differences.

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