One Rep Max Calculator
Lifting 80 kg for 5 reps estimates a one-rep max of about 93 kg using the Epley formula. Brzycki and Lander give slightly different answers, and the gap widens as reps increase — estimates based on more than about 10 reps become unreliable. Below that, the figure is accurate enough to plan training loads.
What is One Rep Max Calculator?
One-rep max is the heaviest weight you can lift once with good technique. It is the reference point for most strength programmes, which prescribe work as a percentage of it.
Estimating rather than testing is safer and more practical for most people. Testing a true one-rep max requires experience, correct technique and a spotter.
All formulas lose reliability at higher rep counts, because how quickly fatigue accumulates varies far more between individuals than the equations assume.
How to use this calculator
- Choose metric or imperial.
- Enter the weight you lifted.
- Enter how many clean reps you completed.
- Pick a formula — Epley is the default.
- Use the percentage table to set your working weights.
How one-rep max is estimated▾
Three published equations are shown. Epley is the most widely used and assumes each additional rep is worth roughly 3.3% of the load. Brzycki curves more steeply at higher reps. Lander was fitted from Olympic lifting data. They agree closely at low reps and diverge above about ten.
Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Lander: 1RM = 100 × weight ÷ (101.3 − 2.67123 × reps)Source: Epley (1985); Brzycki (1993); Lander (1985).
Frequently asked questions
Which formula is most accurate?▾
Epley is the standard choice and performs well up to about 10 reps. Above that all three diverge noticeably, so treat the estimate with caution.
How many reps should I use to estimate?▾
Three to five reps gives the most reliable estimate. Ten or more introduces enough fatigue variation to make any formula shaky.
What percentage should I train at?▾
It depends on the goal: 80–90% for strength, 65–80% for muscle growth, 55–70% for muscular endurance. The table below your result gives specific weights.
Is testing a real one-rep max safe?▾
It carries real risk without proper technique, warm-up and a spotter. Most recreational lifters are better off estimating and working in the 3–5 rep range.
Related calculators
References & method
- Epley (1985); Brzycki (1993); Lander (1985).
Every formula, its published source and its assumptions are listed on our methodology page. This page is written for information and has not been reviewed by a clinician.
Read the methodology →These figures are estimates from population formulas, not medical advice. Individual needs vary. If you are pregnant, managing a medical condition, or under 18, talk to a doctor before changing your diet.