Five zones. Smarter training.
Type your max heart rate and resting heart rate. We compute your 5 training zones using the Karvonen reserve formula.
Standard %-of-max-HR calculations ignore the variation between resting heart rates. The Karvonen formula uses heart-rate reserve (HRR = max − resting) and adds the resting HR back in. zoneHR = restingHR + HRR × percent. A more accurate model than plain %max for runners with non-average resting rates.
| Zone | % HRR | BPM range | Use case |
|---|---|---|---|
| Z1 Recovery | 50-60% | 125–138 bpm | Easy recovery jog. |
| Z2 Endurance | 60-70% | 138–151 bpm | Long-run base building. |
| Z3 Tempo | 70-80% | 151–164 bpm | Steady aerobic effort. |
| Z4 Threshold | 80-90% | 164–177 bpm | Lactate threshold work. |
| Z5 VO₂ max | 90-100% | 177–190 bpm | Hard intervals, max effort. |
Best measurement: in bed, before getting up, after a normal night’s sleep. Take a 60-second count over 3 mornings and average. Caffeine, alcohol and stress all skew it — measure on quiet days.
The formulas and ranges above are grounded in the following peer-reviewed literature.
The HRR formula this calculator implements: zone HR = restingHR + pct × (maxHR − restingHR).
View on PubMedFoundational paper for the polarized 80/20 model. Endurance athletes train ~80% in Zone 1-2 and ~20% in Zone 4-5 — not in the moderate "Zone 3" middle.
Read paperSource of the 7-zone LTHR-anchored model used by trained endurance athletes when a measured threshold is available.
View bookA field test: warm up well, then run a max-effort 800m or a 3-min hill rep with a chest strap. Your peak HR is your tested max. Lab tests are more accurate. The 220 − age formula is a rough estimate; individual variation can be ±10-15 bpm.
For most amateurs, yes. The %max model assumes everyone’s resting HR is around 60 bpm. If yours is 45 or 75, plain %max gives wrong zones. Karvonen accounts for the difference.
Cycling max HR is typically 5-10 bpm lower than running. Either re-test on the bike, or subtract ~7 bpm from your running max for cycling zones. Don’t just copy across.
Heat raises HR for the same effort by 5-10 bpm — known as cardiac drift. On hot or humid days, cap effort by perceived exertion, not heart rate.