One Rep Max Calculator

How It Works

Your one-rep max (1RM) is the maximum weight you can lift for a single repetition with good form. Knowing your 1RM helps you program training percentages — for example, strength work is typically done at 85-95% of 1RM for 1-5 reps, hypertrophy at 65-80% for 6-12 reps, and endurance at 50-65% for 15+ reps. The Epley formula (weight times 1 plus reps divided by 30) is the most commonly used. The Brzycki formula is more accurate for lower rep ranges (under 10). These estimates are most reliable when you input a set of 3-10 reps — beyond 10 reps, all formulas become less accurate. Always use estimates as guidelines and never attempt a true 1RM without a spotter and proper warm-up.