One Rep Max (1RM) Calculator
Estimate your one rep max using the Epley formula.
Enter the weight lifted and number of reps to find your estimated 1RM and training percentages.
One-rep max (1RM) is the maximum amount of weight a person can lift for exactly one complete repetition with proper form. It is the gold standard measure of absolute strength and is used to calculate training loads across all resistance training programs.
Most widely used estimation formulas:
Epley Formula (most common): 1RM = Weight × (1 + Reps / 30)
Brzycki Formula (more accurate for higher rep counts): 1RM = Weight × 36 / (37 − Reps)
Lombardi Formula: 1RM = Weight × Reps^0.10
Mayhew Formula: 1RM = 100 × Weight / (52.2 + 41.9 × e^(−0.055 × Reps))
All formulas are most accurate when reps are between 3 and 10. Accuracy decreases sharply above 15 reps.
Training load percentages (% of 1RM):
| Goal | % of 1RM | Reps per Set |
|---|---|---|
| Max strength | 90–100% | 1–3 |
| Strength | 80–90% | 3–5 |
| Hypertrophy | 67–85% | 6–12 |
| Muscular endurance | 50–67% | 12–20+ |
Worked example: An athlete performs 5 reps of 225 lb (102 kg) on the bench press.
Epley: 225 × (1 + 5/30) = 225 × 1.167 = 262.5 lb Brzycki: 225 × 36 / (37 − 5) = 225 × 1.125 = 253.1 lb
A conservative estimate gives a 1RM of approximately 255–260 lb. Training at 80% = 204–208 lb for strength sets.
Safety note: Directly testing your 1RM carries injury risk, especially without a spotter. Estimation formulas allow safe strength assessment at submaximal loads. Use direct testing only with proper spotting, thorough warm-up, and a 3–5 day rest period beforehand.