One-Rep Max (1RM) Calculator: Epley, Brzycki and Lombardi

Enter the weight you lifted and reps to failure to estimate your one-rep max with three published equations, plus a percentage table from 50% to 100% for programming.

Estimates work best between 2 and 10 reps. Do not attempt the result without a warm-up and a spotter.

Equations

• Epley: 1RM = w × (1 + r/30) = w × (1 + 0.0333 r)
• Brzycki: 1RM = w ÷ (1.0278 − 0.0278 r)
• Lombardi: 1RM = w × r^0.10

w = weight lifted, r = reps to failure. At one rep, Epley uses the weight itself as the 1RM.

How accurate is it?

LeSuer et al. (1997), testing 67 people, found all equations correlated strongly with measured 1RM but clearly underestimated the deadlift. Mayhew et al. (2008) in women found accuracy differs before and after training. So we show all three and their average instead of one number.

Sources

• LeSuer DA et al. (1997). The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. J Strength Cond Res 11(4):211-213 — compares equations including Epley, Brzycki and Lombardi
• Mayhew JL et al. (2008). Accuracy of prediction equations for determining one repetition maximum bench press in women before and after resistance training. J Strength Cond Res — Table 2: Brzycki, Lombardi and the 0.0333 form

Sources checked: 2026-10-25

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<a href="https://fitdealsarabia.com/en/tools/one-rep-max-calculator/">One-Rep Max (1RM) Calculator: Epley, Brzycki and Lombardi</a> — FitDeals Arabia

FAQ

Which equation is most accurate?

None is always best; accuracy varies by lift and training level. The average is a sensible middle.

How many reps should I use?

Between 3 and 10 reps to failure with good form. Above 10 accuracy falls.

How do I use the percentage table?

Programs prescribe loads as a % of 1RM (e.g. 75%). The table turns that into kg or lb from your estimate.