Calculator · Load
One-rep max (1RM) calculator
Performance education — not medical advice. Stop and seek professional care if you have sharp pain, dizziness, chest pain, or unexplained symptoms.
Estimate 1RM from a submaximal set using Epley and Brzycki formulas. Warm up thoroughly; do not test true maxes if you are untrained or injured.
Your result
Formulas
- Epley:
w × (1 + r/30) - Brzycki:
w × 36 / (37 − r)
Interpreting estimated one-rep max
Estimated 1RM formulas convert a submaximal set into a predicted single. Epley and Brzycki are two widely cited educational equations. They diverge more as reps climb; treat both as planning bands, not competition attempts. Never attempt a true maximal single without appropriate preparation, spotting, and personal readiness.
Formulas assume clean reps near technical failure, not sloppy grinders with large form breakdown. If the eighth rep looks nothing like the first, the estimate is noisier. Prefer sets of about 2–8 reps for load planning; very high-rep sets estimate 1RM poorly for strength programming.
Use estimated 1RM to set percentages for warm-ups, volume work, and progress checks — for example planning a top set near 80–85% for strength blocks. Pair with RPE/RIR so that day-to-day readiness can override a rigid percentage. The companion RPE→%1RM helper on Muslex exists for that reason.
Worked case: 100 kg for five solid reps yields roughly mid-110s on Epley and low-110s on Brzycki. Programming a heavy double near 90% of the lower estimate is usually more conservative than chasing the higher formula. Log both estimates for a few weeks and see which tracks your actual heavy singles better.
The noscript table mirrors common classroom examples for non-JS readers. Continue to the Epley vs Brzycki guide and the load pillar for progression context.
Static Epley vs Brzycki examples (weight × reps)
| Set | Epley estimate | Brzycki estimate |
|---|---|---|
| 100 kg × 5 | Epley ~116.7 kg | Brzycki ~112.5 kg |
| 80 kg × 8 | Epley ~101.3 kg | Brzycki ~97.3 kg |
| 140 kg × 3 | Epley ~154.0 kg | Brzycki ~148.2 kg |
| 60 kg × 10 | Epley ~80.0 kg | Brzycki ~75.0 kg |