One Rep Max Calculator
Estimate your one-rep max from any set using Epley, Brzycki, Lombardi and O'Conner formulas, plus a training percentage table.
About the One Rep Max Calculator
Your one-repetition maximum (1RM) is the heaviest weight you can lift once with proper form. Rather than testing it — which is taxing and carries injury risk — this calculator estimates it from any hard set: enter the weight and the reps you completed, and it returns estimates from the four classic formulas (Epley, Brzycki, Lombardi, O'Conner) plus their average.
The formulas approach the problem differently — Epley adds 1/30th of the weight per rep (w × (1 + r/30)), Brzycki divides by a shrinking factor (w × 36/(37 − r)) — but agree closely below 10 reps, which is where rep-based estimation is most reliable. The tool accepts 1–15 reps and reminds you that accuracy degrades toward the high end.
Below the estimates, a training table converts your 1RM into working weights at 60–95%, with the rep ranges typically programmed at each intensity — the practical use of a 1RM number: strength work at 85%+, hypertrophy around 65–80%, technique and speed work lower.
How to Use the One Rep Max Calculator
- 1Enter the weight you lifted (kg or lb — results use the same unit).
- 2Enter how many clean reps you completed (1–15).
- 3Read your estimated 1RM from four formulas and their average.
- 4Use the percentage table to pick working weights for your program.
Frequently Asked Questions
How is 1RM estimated from reps? A worked example
Lifting 100 kg for 5 reps: Epley gives 100 × (1 + 5/30) = 116.7 kg; Brzycki gives 100 × 36/(37 − 5) = 112.5 kg; Lombardi 100 × 5^0.1 = 117.5 kg; O'Conner 100 × (1 + 5/40) = 112.5 kg. The average — about 114.8 kg — is a solid planning number.
Which 1RM formula is most accurate?
None dominates for everyone: Brzycki tends to fit upper-body lifts and lower reps well, Epley often fits squats and deadlifts slightly better, and individual response varies with muscle fibre makeup and training history. That's exactly why this calculator averages four formulas rather than betting on one.
How many reps should I use for the best estimate?
Fewer is better: sets of 2–6 reps give the tightest estimates, and anything beyond 10 reps drifts because endurance increasingly enters the picture. A hard set of 15 might overestimate or underestimate your true max by 10% or more depending on your fibre type.
How do I use the training percentage table?
Multiply your 1RM by the intensity your program calls for. With a 115 kg estimated max: 5×5 at 80% means working sets of 92 kg; a hypertrophy block at 70% for sets of 12 means 80.5 kg; heavy triples at 90% mean 103.5 kg. The table does these multiplications for you.
Should beginners test their true 1RM?
Generally no — maximal attempts require stable technique under heavy load, and beginners' estimated maxes rise so fast the number is stale within weeks. Train off rep-based estimates for the first several months, and when you do test a real max, use a spotter, safety pins and a full warm-up progression.