1RM Calculator

Most 1RM calculators are accurate within 5-10% for rep ranges of 1-10. Accuracy decreases with higher rep counts (above 10 reps). The Epley and Brzycki formulas tend to agree closely for low reps but diverge at higher reps. For best accuracy, use a 3-5 rep max test rather than a 10+ rep set.

The Epley formula (1RM = weight x (1 + reps/30)) tends to predict slightly higher values at lower rep ranges. The Brzycki formula (1RM = weight x 36/(37-reps)) tends to predict slightly lower values. Both are well-validated. The calculator averages both for the most reliable estimate. The difference is usually less than 5%.

For maximum strength: 85-100% for 1-5 reps. For strength and power: 80-90% for 3-6 reps. For hypertrophy (muscle growth): 65-80% for 6-12 reps. For muscular endurance: 50-65% for 12-20+ reps. Most training programs use a mix of these ranges, periodized across training cycles.

Most strength coaches recommend testing 1RM every 8-12 weeks, typically at the end of a training cycle. Testing too frequently is fatiguing and does not give your body enough time to adapt. Between tests, use this calculator with your training sets to estimate progress. Novice lifters can test more frequently as their gains come faster.

True 1RM testing carries higher injury risk than regular training. Always use a competent spotter, warm up thoroughly with progressively heavier sets, and stop if form breaks down. For most people, a 3-5 rep max with this calculator is safer and nearly as informative. Never attempt a 1RM when fatigued, injured, or without proper equipment.

Strength standards vary by body weight, gender, age, and training experience. For an average adult male, bodyweight bench press (1x bodyweight) is a common intermediate goal. Advanced: 1.5x bodyweight. Elite: 2x bodyweight. For women, these ratios are typically 0.5x, 1x, and 1.25x bodyweight respectively. These are guidelines, not requirements.