One Rep Max (1RM) Strength Calculator
Estimate your 1RM (one rep max) from any submaximal lift, plus calculate training percentages for any rep range.
1RM Estimation Guide
1RM Estimation Formulas
Several validated formulas estimate 1RM from submaximal lifts: Brzycki: 1RM = weight × 36 / (37 − reps). Most widely used. Most accurate for 2-10 reps. Epley: 1RM = weight × (1 + reps/30). Simpler. Slightly higher estimates than Brzycki at higher reps. Lombardi: 1RM = weight × reps^0.10. Useful for very high rep ranges. Wathan: 1RM = weight × 100 / (48.8 + 53.8 × e^(-0.075 × reps)). Most complex but well-validated. Best practice: average 2-3 formulas. Estimates become less accurate above 10 reps
Why Reps in Reserve Matters
1RM estimates assume the set was taken to technical failure (RIR 0). If you stopped with reps in reserve: actual 1RM is higher than estimate. Adjustment: count the set as if it was at failure. If you lifted 100kg × 8 with 2 RIR: equivalent to 10 reps at 100kg to failure. 1RM ≈ 100 × 36/27 = 133kg (using Brzycki for 10 reps). RIR-based RPE scale (Mike Tuchscherer): RPE 10 = no RIR (true failure). RPE 9.5 = could grind out half a rep. RPE 9 = 1 RIR. RPE 8 = 2 RIR. RPE 7 = 3 RIR. RPE 6 = 4-5 RIR. M
Training Percentages
Standard percentages of 1RM for different training goals: 1 rep at 100% (true 1RM test). 2-3 reps at 90-93% (strength testing). 3-5 reps at 85-90% (max strength). 5-8 reps at 75-85% (strength + hypertrophy mix). 8-12 reps at 65-75% (hypertrophy primary). 12-15+ reps at 55-65% (endurance, hypertrophy). Below 55%: speed/power work or warm-up. Working sets typically 70-85% for general strength training. Powerlifting peaking blocks: progress to 85-92.5% in the final weeks before testing. Hypertrophy
1RM Testing Protocol
When to test: end of training block. Adequately rested (3-7 days reduced training before test). Familiar with the lift. Warm-up protocol (example for bar squat with target 200kg): 1. Empty bar × 10. 2. 60kg × 5. 3. 100kg × 3. 4. 140kg × 2. 5. 170kg × 1. 6. 185kg × 1. 7. 200kg × 1 (target). 8. Optional: attempt 205-210kg if first attempt was easy. Rest 3-5 minutes between heavy attempts. Adequate spotters and safety equipment. Powerlifting competitions: standardised technique requirements. Practi
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