| Intensity | Target HR (bpm) | Zone |
|---|
| % of 1RM | Weight |
|---|
((HRmax − HRrest) × intensity) + HRrest, with HRmax either 220 − age or the value you type. One-rep max is estimated two ways — Epley weight × (1 + reps/30) and Brzycki weight × 36/(37 − reps) (Brzycki only for reps under 37) — then averaged. Training estimates, not a lab VO₂ or a tested 1RM.
Target heart rate zones use the Karvonen method: ((HRmax − HRrest) × intensity) + HRrest — a formula that factors in your resting heart rate, not just your maximum, giving a more personalized training zone than simpler percentage-of-max methods.
HRmax defaults to the common estimate of 220 minus your age, though you can enter your own measured or tested maximum heart rate instead if you know it, since the age-based formula is a population average and can be noticeably off for any given individual.
One-rep max (1RM) is estimated two different ways from a submaximal set: the Epley formula (weight × (1 + reps/30)) and the Brzycki formula (weight × 36/(37 − reps), only valid for reps under 37), then the two estimates are averaged together. Both are well-established training estimates, not a substitute for an actual tested 1RM or a lab-measured VO2 max.
Because it calculates your heart rate reserve (max minus resting) and scales your target zone from that reserve, rather than a flat percentage of your max alone — this accounts for individual differences in resting heart rate, giving a more personalized training zone.
Use your own tested maximum heart rate if you have one from an actual maximal exercise test — it's more accurate for you individually. The 220-minus-age formula is a widely used population average, but can be off by quite a bit for any specific person.
Epley and Brzycki are both well-established formulas that estimate 1RM slightly differently based on your weight and reps performed. Averaging them tends to smooth out the small discrepancies between the two, giving a more balanced overall estimate.
They're reasonable training estimates based on submaximal performance, but not a substitute for an actual tested 1RM under controlled conditions, which accounts for individual factors like technique and fatigue that a formula can't capture.