Health Calculators
One Rep Max Calculator
Your one-rep max is the most you could lift for a single repetition. Instead of testing it, which is the riskiest set in the gym, estimate it from a set you have already performed: the weight lifted and the reps completed are enough for the Epley, Brzycki and Lombardi formulas.
Calculator
Formula
Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki: 1RM = weight × 36 ÷ (37 − reps). Lombardi: 1RM = weight × reps ^ 0.10. All three are estimates fitted on sets of roughly 1 to 12 reps, which is why the calculator marks anything above 12 reps as an extrapolation.
About This Calculator
What It Does
This calculator estimates a one-rep maximum, the most you could lift once, from a set you have already performed. Enter the weight lifted and the reps you managed, choose the unit, and it returns the estimate from the Epley, Brzycki and Lombardi formulas side by side, with the chosen formula as the headline and a table reading the same weight at 1 to 12 reps.
Worked Example
The page opens on 100 kg lifted for 5 reps, in kilograms, with Epley as the headline formula. Epley gives 100 × (1 + 5 ÷ 30) = 116.67 kg; Brzycki gives 100 × 36 ÷ 32 = 112.5 kg; Lombardi gives 100 × 5 ^ 0.10 = 117.46 kg. The three sit within 5 kg of one another, which is the honest width of the estimate. Switch the unit to pounds and the same set reads 220.462 lb: the unit control converts the load rather than relabelling it, so the physical weight never moves.
Real-World Usage
Use it to plan a training block without testing a true single, to turn a set you actually did into a working load, to compare the three formulas before choosing one for your own programming, or to see how far a high-rep set can be pushed before the estimate stops being credible.
Local Context
The three formulas are the same everywhere, so this page carries no country-specific rules. What does vary is the gym: plates are metric in most of the world and in pounds in the United States, which is why the calculator offers both units and converts the load rather than the number. An estimate is not a competition attempt — the only true one-rep max is a lift you have made under judging.
Last reviewed: October 2026.
Frequently Asked Questions
How do I estimate my one-rep max?
Lift a weight you can manage for a few reps, then put both numbers into a formula. A 100 kg set of 5 reps reads 116.67 kg on Epley, 112.5 kg on Brzycki and 117.46 kg on Lombardi, so read the three together rather than trusting one of them alone.
Which of the three formulas should I use?
Epley is the most widely used and sits between the other two around five reps. Brzycki turns more conservative as the rep count rises, because its divisor falls, and Lombardi is the flattest of the three. This page shows all three so the spread stays visible.
How many reps should I use for a reliable estimate?
Between 3 and 8. The formulas are fitted on sets of roughly 1 to 12 reps; at 1 or 2 reps the estimate is close to the weight itself, and past 12 the arithmetic drifts away from what the published data supports.
What is the difference between a one-rep max and a training max?
A one-rep max is the most you can lift once; a training max is a working figure, usually about 90 per cent of it, used to set loads you can train week after week. A rep-based estimate is normally read as an input to the training max, not as a competition attempt.
Related Tools
Lean Body Mass Calculator
Estimate your lean body mass and fat mass from your weight and body-fat percentage, read the fat-free mass index against reference values, and compare the Boer, James and Hume estimates.
Body Fat Calculator
Estimate your body-fat percentage from tape measurements with the U.S. Navy method, or from BMI when you have no tape.
BMI Calculator
Calculate your Body Mass Index (BMI) and understand your weight category.