Estimate your true one-rep max from any weight and rep range, using six proven strength formulas.
| % of 1RM | Weight | Typical Use |
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Enter the weight you lifted and the number of clean reps you completed (without failing form), and the calculator estimates your theoretical one-rep max using six widely used strength formulas, then averages them for a balanced estimate. It also generates a training percentage chart so you know exactly what weight to load for strength, hypertrophy, or endurance work.
Every 1RM formula is an approximation built from population averages, and each one tends to drift at different rep ranges. Epley and Brzycki are the most widely cited and tend to agree closely under 10 reps. Lombardi, O'Conner, Wathan, and Mayhew offer alternative curves that can correct for individual variation. Averaging across all six smooths out the quirks of any single formula.
1RM formulas are calibrated on rep ranges typically between 1 and 10. Past 10 reps, muscular endurance and fatigue resistance start to influence the set more than raw strength, so the estimate becomes less reliable. For the most accurate 1RM estimate, test with a weight you can lift for 3–6 reps.
No single formula is universally most accurate — accuracy varies by individual, exercise, and rep range. The Epley formula tends to slightly overestimate at higher rep counts, while Brzycki tends to be more conservative. Using the average of multiple formulas, as this calculator does, generally produces a more reliable estimate than relying on just one.
Estimated 1RM is useful for programming, but testing a true 1RM carries injury risk, especially for compound lifts like squat and deadlift. Most lifters get equivalent training value from working off an estimated 1RM and adjusting based on how the prescribed weight actually feels.
Lower percentages (50–65%) are typically used for warm-ups and technique work. Moderate percentages (65–80%) target hypertrophy and muscle growth. Higher percentages (80–95%) build maximal strength. Percentages above 95% are generally reserved for peaking phases close to competition or testing.