Estimated one-rep max from a weight and 1-12 reps using the Epley, Brzycki, and Lombardi formulas, with a percentage loading table for training.
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FORMULA USEDOne Rep Max Calculator
What a one-rep max is
Your one-rep max (1RM) is the heaviest weight you can lift once with good form — the anchor number strength programs are built around, because training loads are prescribed as percentages of it. Testing it directly every week would be exhausting and risky, so lifters substitute a hard set of 1–12 reps and let a formula stretch it to a single.
Three named formulas
Epley (1985): w × (1 + reps ÷ 30) — the most common gym default, moderately generous at higher reps. Brzycki (1993): w × 36 ÷ (37 − reps) — a touch more conservative and accurate near low reps. Lombardi: w × reps0.10 — a power-law mapping that runs highest of the three at mid reps. The board shows all three plus their spread, and the loading table rounds each percentage of 1RM to the nearest 2.5 so every load is actually loadable with plates.
Using the percentage table
Classic strength blocks live between 60% and 95%: hypertrophy work around 65–75% for 8–12 reps, strength work at 80–90% for 3–5 reps, and singles at 90–95% reserved for peaking weeks. Percentages make programs portable — when your estimate rises, every load in the plan rises with it.
Training table: 80% of 262.5 = 210 lb for strength sets; 70% = 182.5 lb for volume work.
How to use it
Pick pounds or kilograms.
Enter the weight and rep count of a genuinely hard, clean set (1–12 reps).
Read the Epley estimate, then compare Brzycki and Lombardi for spread.
Pull training loads from the percentage table and round to your real plates.
Frequently asked questions
What is One-Rep Max (1RM)?
The heaviest load you can lift for exactly one repetition with proper form. It is the reference point strength programs use — training weights are written as percentages of it, so knowing (or estimating) your 1RM turns any program into actual plate math.
How accurate are 1RM calculators?
Within about 5% for trained lifters working from sets of 10 reps or fewer, which is why this tool shows three formulas side by side rather than one confident number. Accuracy falls off sharply at high reps, with unpracticed lifts, and with grindy reps versus crisp ones.
What rep ranges work best for 1RM estimation?
Three to eight reps is the sweet spot, using a weight you could not have repeated. Single reps are exact by definition but risky to test often; anything past 10 reps estimates muscular endurance more than maximal strength, and the three formulas visibly disagree there.
How often should I test my actual 1RM?
One to three times a year at the end of a training block, fully rested and with spotters or safety pins in place. Between tests, re-estimate from a hard 3–5 rep set every few weeks — that is the whole point of the formulas.
What training percentages should I use?
Common bands: 60–70% for technique and volume work, 70–80% for hypertrophy in the 8–12 rep range, 80–90% for strength in the 3–5 rep range, and 90–95% singles only when peaking for a max or competition. The table gives the exact loads for each band.
Is it safe to train at 100% of my 1RM?
Max-out attempts belong at the end of a peaking block, with spotters, safeties, and a reason — a competition or a planned test. Routine training at 100% mostly accumulates fatigue and injury risk; the table stops at 95% because progress is built at lower percentages.