One-Rep Max Calculator (1RM)
Your estimated one-rep max from any set, and the weights for every rep range.
Good to know. An estimated max is a planning number. Testing a true one-rep max is best left for a spotter and a good day.
Approximate. Real-world values vary.
How it works
In plain words
The Epley formula adds one thirtieth of the weight for each rep you did: the more reps, the heavier your single-rep max. Brzycki and Lombardi are two other common formulas, shown for comparison.
The formula
Epley: 1RM = weight × (1 + reps ÷ 30) Brzycki: 1RM = weight × 36 ÷ (37 − reps) Lombardi: 1RM = weight × reps^0.1
Worked example
100 kg for 5 reps: 100 × (1 + 5 ÷ 30) = 116.7 kg estimated one-rep max. Brzycki gives 112.5 kg.
Sources
- Brzycki, Strength testing: predicting a one-rep max from reps-to-fatigue, Journal of Physical Education, Recreation and Dance, 1993 The Brzycki formula.
- Epley, Poundage Chart, Boyd Epley Workout, 1985 The Epley formula.
- LeSuer et al., The accuracy of prediction equations for estimating 1-RM performance, Journal of Strength and Conditioning Research, 1997 How the formulas compare.
Sources checked September 30, 2026. 3 automated tests check its answers on every change.
About the one-rep max calculator (1RM)
Your one-rep max, or 1RM, is the heaviest weight you can lift once with good form. Strength programmes use percentages of it to set training weights, but testing a true max is tiring and carries some risk. Estimating it from a set of several reps is safer and nearly as useful.
Enter the weight and how many reps you managed, to failure or close to it. The Epley formula, the most widely used, is the main result; Brzycki and Lombardi, two other well-known formulas, are shown for comparison. They agree closely around 5 reps and drift apart as the reps go up, so sets of 2 to 10 give the best estimate.
The table turns your estimated max into working weights: roughly 85% for sets of 5, 75% for 10 and 70% for 12. Use it to plan sets, or to check progress without testing a single.
Results vary with the exercise and the person. People built for endurance can do more reps at a given percentage than people built for power, and the formulas work best on big lifts like the squat, bench press and deadlift. Round to the plates you have, and warm up well before heavy sets.
Questions people ask
How do I calculate my one-rep max?
Multiply the weight by 1 + reps ÷ 30 (the Epley formula). 100 kg for 5 reps gives about 116.7 kg.
What percentage of my max should I train at?
Around 85% for sets of 5 to build strength, and 65–75% for sets of 8 to 12 to build muscle.
Which one-rep max formula is most accurate?
Epley and Brzycki are both accurate for sets of up to about 10 reps. Beyond that, all formulas get less reliable.