One Rep Max Calculator (1RM)
Calculate your one rep max from any submaximal set. Choose between Epley, Brzycki, and Lombardi formulas.
How it works
Epley: 1RM = weight × (1 + reps / 30). Brzycki: 1RM = weight × 36 / (37 − reps). Lombardi: 1RM = weight × reps^0.10.
Which formula should I use?
Epley is the most common and tends to slightly overestimate at higher rep ranges (8+ reps). Default choice for most lifters.
Brzycki is more conservative and generally more accurate for sets of 1-10 reps. Preferred by powerlifters.
Lombardi is a power-curve formula that gives different results, particularly accurate for low-rep sets. Good for cross-checking.
How accurate is 1RM estimation?
Estimates are most accurate for sets of 1-5 reps (within ±5% of true 1RM). At 8+ reps the error widens because muscular endurance becomes a confounding variable. Never use these numbers as a programming target without progressive overload — they are a snapshot, not a prescription.
When should I actually test 1RM?
Most strength programmes use percentages of 1RM. You can usually calculate, programme, and progress without ever testing. Test only when peaking for competition, validating a long-term cycle, or out of curiosity — and never with a beginner who has not built solid technique.