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Calcul du 1RM
Estimate your maximum load from a submaximal test. Safer and more precise than a real test beyond 10 repetitions.
What is 1RM?
The 1RM (One-Rep Maximum) is the maximum weight that you can lift once in a given movement, respecting the technique. This is the universal reference for calibrating programming: all bodybuilding load percentages are expressed as a % of 1RM.
Why not test your real 1RM?
Testing a real 1RM is risky (injury if missed), tiring nervously (3-4 days of recovery), and technically difficult without a spotter. The estimation formulas from a sub-maximal test (3 to 8 repetitions) give a result within ±5% of the true 1RM, in complete safety.
The 4 formulas used
Epley (1985)
1RM = load × (1 + reps / 30)
The most popular, simple. Accurate up to 10 repetitions.
Brzycki (1993)
1RM = load × 36 / (37 − reps)
Slightly more conservative than Epley on high reps. Widely used in scientific literature.
Lombardi (1989)
1RM = load × reps^0.10
Power formula, more stable on very low repetitions (1-3).
O'Conner (1989)
1RM = load × (1 + 0.025 × reps)
Simple linear. Tends to underestimate 1RM compared to others.
Precision and good practice
The higher the number of repetitions, the greater the error. Ideal: 3 to 8 repetitions at maximum effort (impossible to do one more with correct technique). Beyond 10 reps, the error can exceed 10%.
Precision also depends on the movement: more reliable on heavy polyarticular exercises (squat, deadlift, bench press) than on isolation exercises (curl, elevations).
Questions fréquentes
Epley and Brzycki give very similar results on 3-8 repetitions and are the most used. The average of the four formulas reduces the individual error. Beyond 10 reps, all lose precision.
Yes but with less reliability. The formulas have been validated on heavy polyarticular exercises (squat, bench, deadlift). On the isolation exercises, the estimate is correct but the deviation can reach ±10%.
Every 8-12 weeks for an amateur athlete. If you follow a structured program, the 1RM readjusts with each training block (4-6 weeks).
A lot. Hot, rested, fasting or after a coffee, your 1RM can vary by ±5%. For a representative test: complete warm-up, no heavy session the day before, correct hydration.