One-rep max (Epley)

The formula

• 1RM = w · (1 + r / 30)

w is the weight lifted, r the number of repetitions completed with good form, and 1RM the estimated one-repetition maximum in the same unit as the weight. Every repetition beyond the first adds a thirtieth of the weight to the estimate; the source, Epley (1985), is cited under the formula.

Holds when the set is short and taken close to failure. Epley’s chart was built from sets of a few repetitions, and past about ten the estimate drifts upward from what a lifter can actually do once.

A worked example

80 kg for 5 repetitions: 1RM = 80 · (1 + 5 / 30) = 80 · 1.167 = 93.3 kg. The same weight for 10 repetitions gives 80 · 1.333 = 106.7 kg.

Epley and Brzycki

The other common estimate, Brzycki, gives 36 · w / (37 − r): 90 kg for the same 80 × 5. The two formulas meet at exactly 10 repetitions, where both give the weight times 4/3, and part on either side; Epley reads higher above ten and lower below. The one-rep max calculator shows both and a percentage table from their mean.

Working backwards

Turned round, the formula says what to load for a set of r at a share of the max. A lifter with a 1RM of 100 who wants a set of 8 loads 100 / (1 + 8 / 30) = 79 kg. The card above gives the weight, or the repetitions, from the other two.

Common mistakes

• Counting repetitions that were not completed. r is the number finished, not attempted.
• Using a set of fifteen or twenty. The estimate is for short sets; a long set measures endurance.
• Testing on the estimate. A calculated max is a planning figure. An actual maximal attempt needs a spotter and a warm-up, and is not what this page advises.

Frequently asked questions