One-rep max
calculator
No need to grind a true max single — lift a moderate weight for reps and the classic formulas estimate your 1RM. Plus the percentage table your program actually asks for.
Estimating max strength from rep work
The relationship between reps and load is regular enough that a hard set of 3–8 reps predicts a one-rep max surprisingly well. The two standard formulas:
Brzycki: 100×36÷32 = 112.5 kg — the honest range.
Accuracy and limits
Estimates are tightest from low-rep sets taken close to failure; beyond ~10–12 reps the math drifts optimistic, which is why this tool caps at 15. Trained lifters usually land within a few percent; the two formulas bracketing your true max is the realistic picture.
Why estimate at all
Programs prescribe loads as percentages of 1RM — the table above turns your estimate straight into working weights — and testing true maxes is fatiguing and riskier than a hard set of five. If you do test, warm up thoroughly, use spotters or safeties, and keep pristine form. Track bodyweight context with the BMI calculator.
One-rep max FAQ
Lift a weight for as many clean reps as possible (ideally 3–8), then apply a formula: Epley multiplies the weight by 1 + reps÷30. 100 kg for 5 reps estimates about 117 kg.
They were fitted to different data. Epley reads slightly higher at moderate reps; Brzycki slightly lower. Your true max usually sits between them — treat the pair as a range.
Within a few percent for sets of 3–8 reps taken near failure. Accuracy degrades past 10–12 reps and varies by exercise — squat and deadlift estimates run truer than bench for many lifters.
Typical ranges: 85–95% for low-rep strength work, ~75–85% for 5-rep sets, ~65–75% for 8–12-rep hypertrophy work. The table above computes these from your estimate.