One Rep Max Calculator
Estimate your one-rep max (1RM) for any lift from a submaximal weight and rep count, with percentage tables.
Testing a true 1RM carries injury risk, especially without a spotter. Working back from a heavy set of 3–5 reps gives a reliable estimate for most lifters and is the standard approach in programming. I use the 5-rep test for squats, bench, and deadlift at the start of a training cycle to set working weights for the entire program.
1RM estimates from multi-rep sets become less accurate above 6 reps because fatigue and form breakdown affect rep capacity differently than pure strength. For the most accurate estimate, use 1–5 rep sets. At 10+ reps, treat the estimate as a rough guide only.
The major 1RM formulas
Epley (1985): 1RM = Weight × (1 + 0.0333 × Reps). Most commonly used. Slightly overestimates at low reps, more accurate at moderate reps. Brzycki (1993): 1RM = Weight × (36 ÷ (37 − Reps)). Widely used in powerlifting. Tends to be more conservative (lower 1RM estimate). Only valid up to 10 reps. Lombardi (1989): 1RM = Weight × Reps^0.1. Slightly different curve, produces results between Epley and Brzycki for most rep ranges. Using an average of the three formulas reduces the impact of any single formula's biases.
Using 1RM for training percentages
Percentage-based training uses 1RM as the anchor for all working weights. A program might prescribe "4 sets of 5 at 80% of 1RM." With an estimated 1RM of 280 lbs, that's 224 lbs for 5 reps. Standard training percentages: 60–70% for conditioning work, 70–80% for hypertrophy, 80–90% for strength, 90–100% for peaking and testing. These percentages represent approximately the maximum sustainable effort for the given rep range.
1RM accuracy considerations
1RM estimates are approximations with individual variation. Some lifters are more "rep efficient" than others, some can complete 10 reps at 75% of their true 1RM while others can only manage 7–8. Training history, movement efficiency, muscle fiber composition, and fatigue all affect how well submaximal rep counts predict true maximum. Use the estimate as a starting point and adjust based on how training weights feel.
Frequently asked questions
How often should I test my 1RM?
Most strength programs include a testing week at the end of a training block (typically every 8–16 weeks). More frequent 1RM testing produces more current data but increases injury risk and disrupts training. Estimating from submaximal sets every few weeks gives a running estimate without the risk or disruption.
Is it the same for all lifts?
The formulas are lift-agnostic, but accuracy varies. The squat and bench press have the most research validation. Deadlift estimates tend to be less accurate because technique and mental factors affect single maximal efforts more. Olympic lifts (clean, snatch) are very technique-dependent, 1RM estimates from multi-rep sets are less reliable.