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

You rarely need to actually attempt a true one-rep max to know roughly what it is β€” a submaximal set and a formula gets you close.

Why estimate instead of testing directly

A true 1RM attempt carries real injury risk, especially for less experienced lifters, and requires a lengthy warm-up and recovery process. Estimating from a lighter, higher-rep set most people can safely perform is the practical everyday alternative.

Epley formula: 1RM = weight Γ— (1 + reps Γ· 30)

Lifting 200 lb for 5 reps gives an estimated 1RM of 200 Γ— (1 + 5/30) β‰ˆ 233 lb. Epley tends to estimate slightly higher than Brzycki, especially at higher rep counts.

Brzycki formula: 1RM = weight Γ— 36 Γ· (37 βˆ’ reps)

The same 200 lb for 5 reps gives 200 Γ— 36 Γ· (37βˆ’5) = 225 lb under Brzycki. The two formulas agree closely at low rep counts but diverge more as reps climb.

Both formulas are most accurate under about 10 reps

Estimation formulas assume a fairly direct relationship between reps and fatigue that holds reasonably well from 1 to around 10 reps, but accuracy drops noticeably for higher-rep sets, since endurance factors start to matter more than raw strength.

Use your 1RM estimate to build a training percentage table

Once you have an estimated 1RM, common training percentages follow directly: roughly 90% for 3-5 rep strength work, 75-80% for 8-10 rep hypertrophy work, and 60-65% for lighter technique or warm-up work.

Why two formulas can give different answers for the same set

Epley and Brzycki were both derived from different sets of lifting data and use different mathematical relationships between reps and load. Neither is definitively "more correct" β€” many lifters average the two estimates, or simply pick one formula and track progress consistently with it over time.

An estimated 1RM is a planning tool, not a competition number

These formulas assume a consistent effort-to-failure relationship that varies somewhat by exercise, by individual, and by how close to true failure the set actually was. Treat the result as a useful number for programming training percentages, not as a guaranteed number you could actually lift once.

Frequently Asked Questions

Which formula is more accurate, Epley or Brzycki?

Neither is universally more accurate β€” they tend to agree closely within about 1-5 reps and diverge more from there, with Epley usually estimating slightly higher at higher rep counts. Many programs simply pick one and use it consistently.

Can I use a 1RM estimate from a set of 15+ reps?

You can, but accuracy drops substantially at very high rep counts, since muscular endurance starts influencing the number more than raw single-rep strength. A set of 3-8 reps generally gives a more reliable estimate.