One Rep Max Calculator

The Epley formula is the usual starting point: 1RM = weight × (1 + reps ÷ 30). A set of 100 kg for 10 reps gives 100 × (1 + 10/30) = 133 kg. Brzycki, which uses weight × 36 ÷ (37 − reps), gives the same answer at 10 reps but diverges from Epley at other rep counts.

Reasonably good for sets of about three to six reps, and progressively worse above that. All these formulas were fitted to group averages, mostly on the bench press and squat in trained lifters, so they transfer poorly to isolation exercises and to the deadlift, and they overestimate for people who can grind out high-rep sets. Expect the true value to sit within roughly 5% of the estimate on a familiar barbell lift, and further out otherwise.

There is no single winner. Brzycki tends to read low on high-rep sets while Epley reads high; Wathen and Lombardi sit between them. Studies comparing them find the differences are small relative to day-to-day variation in how strong you feel, which is why this tool shows all five and averages them.

Because a single is already a 1RM — there is nothing to estimate. Epley and Wathen do not actually return the input weight when you feed them one rep, so this tool handles that case explicitly rather than showing a wrong number.

Only if you have a real reason to, and only with proper preparation. A true max attempt is the highest-risk lift in the gym: it needs a thorough warm-up, technique you can hold under load, and safety bars or a competent spotter. Beginners, anyone with a current injury and anyone with a heart or blood-pressure condition should talk to a clinician or coach before attempting one.

Around eight for most trained lifters, which is the conventional NSCA reference point used in the table on this page. Your own number depends heavily on the exercise, your training history and how close to failure you take the set — some people manage twelve reps at 80% on a leg press and six on a bench press.