e1RM range calculator

Enter one set. Get four named estimates of your one-rep max, how far apart they are, and a plain warning when the set is the kind these formulas handle badly.

A one-rep max estimate (e1RM) turns a set like 225 × 5 into a guess at your best single. Different formulas give different answers, so this page shows all four side by side instead of one confident number.

Estimates modeled

Estimated one-rep max

about 253 to 264 lb

Middle of the four formulas: 257.8 lb. Based on 5 reps to failure (reps + RIR).

Formula	Estimate
Epley	262.5 lb
Brzycki	253.1 lb
Lombardi	264.3 lb
O'Connor	253.1 lb

The formulas

Epley: w × (1 + r ÷ 30)
Boyd Epley, "Poundage Chart" (1985), a coaching chart, not a peer-reviewed study. The Program Builder uses this form.
Brzycki: w × 36 ÷ (37 − r)
Matt Brzycki, a practitioner source; we have not read the original. Form checked against the methods of Abdul-Hameed 2012.
Lombardi: w × r^0.10
Form as commonly listed; we have not checked the original source.
O'Connor: w × (1 + 0.025 × r)
Form as commonly listed; we have not checked the original source.

r = reps completed + RIR; w = weight. We stop estimating above 15 reps to failure; that cutoff is ours, not from a study.

Limits

These are population formulas modeled, not your own strength curve. The spread shows how much the formulas disagree; it is not a margin of error.
Head-to-head tests are small and lift-specific. In 20 trained adults benching at 70% of their max, Epley had the smallest error of the formulas tested (Nickerson 2020). In 26 men doing a prone bench pull, the Lombardi and O'Connor formulas overestimated by about 3 to 4% (García-Ramos 2019).
Fewer reps to failure give better estimates; above 10, treat the number loosely (Reynolds 2006).
RIR is a self-rating self-reported. It is more accurate close to failure, and the research is mostly on young trained men doing barbell lifts. Machines, isolation lifts and beginners are less studied.
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