What is a one-rep max?
Your one-rep max (1RM) is the most weight you can lift for a single, full repetition with solid technique. It's the anchor that strength programs are built around: instead of guessing, you train at a percentage of your max — for example, sets of five at 80% — so the load is hard enough to drive progress without being reckless.
How the estimate works
Testing a true 1RM is fatiguing and, for many lifters, risky. A safer approach is to lift a sub-maximal weight for a few clean reps and estimate the max from that. This calculator averages several established formulas — Epley, Brzycki, Lombardi, and O'Conner — to even out the small differences between them:
- Epley: weight × (1 + reps ÷ 30)
- Brzycki: weight × 36 ÷ (37 − reps)
Accuracy is best at low rep counts. Aim to test with a weight you can do for 3–6 reps; beyond ~10 reps the estimate drifts because endurance starts to matter as much as raw strength.
Turning your max into a program
Once you know your estimated max, you can put it to work. Want a full routine built around the right percentages and rep ranges for your goal? Build a free program in about 30 seconds.
Estimates only. Use proper warm-ups, a spotter or safeties for heavy lifts, and stop if technique breaks down.