One Rep Max Calculator
Last updated: June 2026 · Free · No sign-up required
Enter values above and click Calculate to see your result instantly.
Quick reference
Training percentages of 1RM:
| % of 1RM | Reps | Use |
|---|---|---|
| 100% | 1 | Max strength test |
| 90% | ~4 | Strength |
| 80% | ~8 | Strength + size |
| 70% | ~12 | Hypertrophy |
| 60% | ~15+ | Endurance |
monitor_weight A starting point, not a diagnosis
This calculator gives you the same number a clinician would compute by hand from your inputs. It is informational, never a substitute for a doctor. If a result surprises you, write it down and discuss it at your next appointment — that conversation is the goal, not a verdict from a webpage.
science Built from peer-reviewed formulas
Every health calculator on CalcaTools uses an equation from the WHO, NIH, ACOG, CDC, or a published peer-reviewed paper. The exact citation is in the "Formula & methodology" section. We re-check sources quarterly and update the page when guidance changes — the "Last reviewed" date is at the top.
volunteer_activism Designed for real people
Health calculations only help if you can actually use them. We use plain-English labels (no jargon), accept both metric and US units, and show what a "normal" range looks like alongside your result — so you understand what the number means, not just what it is.
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Your weight, height, age, pregnancy details, and any other health input never leave your browser. Calculations run client-side; nothing is logged or stored on our side. We don't want your medical data — we just want the formula to work for you.
Interpretation guide
1RM formulas:
| Formula | Equation |
|---|---|
| Epley | w x (1 + reps/30) |
| Brzycki | w x 36 / (37 - reps) |
| Lombardi | w x reps^0.10 |
Formula & methodology
Formula: Epley 1RM = weight x (1 + reps / 30); best accuracy at <= 10 reps
Your one-rep max is the most weight you can lift once with good form. Rather than testing it directly (which is risky), the calculator estimates 1RM from a submaximal set using formulas like Epley and Brzycki. Accuracy is best at 10 reps or fewer. From your 1RM you can program training loads — for example sets at 70–85% for muscle growth or 90%+ for peak strength.