1RM Calculator

Your one-rep max is the maximum weight you can lift for exactly one full repetition with proper form on a given exercise. It's the standard measure of absolute strength and the foundation for setting percentage-based training loads across every rep range.

Expect a real-world variance of around ±5–10%. Accuracy is highest for sets of 3–6 reps performed close to failure. It decreases with higher rep counts (10+ reps) and on technique-heavy lifts like the squat and deadlift. Use it as a reliable training guide, not a definitive number.

Multiply your estimated 1RM by the target percentage for your rep range. Training at 85–95% (1–3 reps) develops maximal strength. 70–85% (4–6 reps) builds strength and power. 60–75% (7–12 reps) drives hypertrophy. The loading breakdown table on this page calculates exact weights for every rep range automatically.

The hypertrophy range — roughly 6–12 reps at 65–80% of 1RM — produces the strongest muscle growth stimulus per set when taken close to failure. Lower rep work (1–5 reps) builds strength and neural efficiency; both contribute to hypertrophy but are less efficient for that goal specifically. Effective programs train across multiple rep ranges.

Every 6–12 weeks is sufficient for most lifters — typically at the end of a training block. Rather than maxing out directly (which carries injury risk without proper peaking prep), use a heavy working set with this calculator as a safer, ongoing measure of progress. If your performance-based estimate is climbing, you're getting stronger.

Both are reliable for sets of 3–10 reps. Brzycki tends to be slightly more accurate at lower rep ranges (1–5 reps); Epley handles wider rep ranges better. This calculator averages both formulas when your set falls within 10 reps to reduce single-formula prediction error. Above 10 reps, Epley alone is used as Brzycki becomes unreliable at high rep counts.