One-Rep Max (1RM)
How much could you lift for one single repetition? Lift a weight you can handle for a few clean reps, and the heaviest load follows from how many reps you managed. Works for the bench press, squat, deadlift and most other lifts — without having to test a true maximum.
Why Reps Tell You Your Maximum
A muscle can lift a light weight many times but its heaviest weight only once. Between those extremes the number of reps you can do falls in a steady, predictable way as the load goes up: roughly 2–3% less weight for every extra rep. Count your reps and you can work back to the weight you could lift once.
The formulas were fitted to many lifters and agree well up to about 10 reps. People with mostly fast-twitch muscles or a lot of practice at heavy singles can lift more than predicted; endurance athletes often less.
From Your Set to One Rep, Step by Step
1RMRep-Max Table
EpleyThe heaviest weight for each number of reps, from your estimated 1RM. Round to the plates you have.
All Seven Formulas
The same set in the seven best-known formulas. Where they agree, the estimate is solid; a wide spread means the set had too many reps to be precise. In a study of 67 students, Mayhew and Wathan predicted the bench press best and Wathan the squat; all seven underestimated the deadlift by about 9–14%.
Key Relations
Weight w lifted for r reps. Every rep adds 1/30 (3.3%) of the weight. The most widely used formula.
A little lower than Epley above a few reps; often used for the bench press. Not meant for more than about 10 reps.
Turning the formula around gives the heaviest weight for any number of reps: the rep-max table.
Sources & Verification
- B. Epley, Poundage chart, Boyd Epley Workout, Lincoln NE: Body Enterprises (1985).
- M. Brzycki, “Strength testing — predicting a one-rep max from reps-to-fatigue”, Journal of Physical Education, Recreation & Dance 64(1), 88–90 (1993).
- J. LeSuer, J. McCormick, J. Mayhew, R. Wasserstein & M. Arnold, “The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift”, Journal of Strength and Conditioning Research 11(4), 211–213 (1997) — the seven formulas compared (Epley, Brzycki, Lander, Lombardi, Mayhew et al., O’Conner et al., Wathan).
Frequently Asked Questions
How do I calculate my one rep max?
Lift a weight for as many clean reps as you can (best 2 to 10), then use the Epley formula: 1RM = weight × (1 + reps ÷ 30). For 100 kg × 5 reps that is 100 × (1 + 5/30) = 116.7 kg. The Brzycki formula, weight × 36 ÷ (37 − reps), gives 112.5 kg for the same set.
Which one rep max formula is the most accurate?
For sets of up to about 10 reps the common formulas agree within a few percent; Epley and Brzycki give exactly the same answer at 10 reps. In a study of 67 students (LeSuer et al., 1997) the Mayhew and Wathan formulas predicted the bench press best and Wathan the squat, while all formulas underestimated the deadlift by about 9 to 14%. Above 10 reps they drift apart and all become less reliable. The calculator shows all seven side by side, so you can see how much they agree for your set.
What percentage of my 1RM is 5 or 10 reps?
With the Epley formula, the heaviest weight you can lift 5 times is about 86% of your one-rep max, 8 reps about 79% and 10 reps 75%. Each extra rep costs roughly 2 to 3% of the weight. The rep-max table lists 1 to 12 reps for your own 1RM.
Does the 1RM calculator work for bench press, squat and deadlift?
Yes. The formulas were tested on the bench press, squat and deadlift and work for most other lifts too. Use a set with good form taken close to failure; a set stopped well before failure underestimates your maximum.
Should I test my one rep max for real?
It is not needed: an estimate from a set of 3 to 5 reps is close and much safer. If you do test a true single, warm up well, build up in small steps and use a spotter or safety bars.