Karvonen Heart Rate Zones Calculator
Target HR = ((max HR − resting HR) × intensity) + resting HR. The HRR (heart rate reserve) method.
Result
Heart rate reserve (HRR)
125 bpm
Max 185 − rest 60. Target zones below.
- Z1 50-60% Recovery123-135 bpm
- Z2 60-70% Aerobic base135-148 bpm
- Z3 70-80% Tempo148-160 bpm
- Z4 80-90% Threshold160-173 bpm
- Z5 90-100% VO2 max173-185 bpm
- Resting HR60 bpm
- Max HR185 bpm
Step-by-step
- HRR = max HR − resting HR = 185 − 60 = 125.
- Target HR @ X% = HRR × X + resting HR.
- Example Z2 lower: 125 × 0.6 + 60 = 135 bpm.
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
% 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.
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