One-Rep Max (1RM) Calculator
Estimate your maximum single-rep strength from any training weight and rep count using three proven formulas.
100% client-side · no upload
Epley (most common)
Brzycki
Lombardi
How to use
- Enter the weight you lifted in kilograms.
- Enter the number of reps you completed with that weight (best accuracy at 2–10 reps).
- Click Calculate 1RM to see your estimated one-rep max from three formulas.
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- Training Load Calculator — session RPE × duration stress
- Workout Builder — plan sets, reps, and rest periods
- Gym Rest Timer — countdown timer between sets
- Sleep vs Recovery Score — gauge readiness before training
よくある質問
- Is this 1RM calculator free?
- Yes, completely free with no signup and no usage limits.
- Does my data leave my device?
- No. All calculations run in JavaScript inside your browser. Nothing is sent to any server.
- Does it work on mobile?
- Yes. The calculator is mobile-first and works on iPhone Safari and Android Chrome.