One Rep Max Calculator

One rep max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It's a key metric for measuring strength and planning training programs. Rather than testing your actual 1RM (which can be risky), you can estimate it from the weight and reps of a lighter set.

Most formulas are accurate within 5-10% when using 3-10 reps. Accuracy decreases with higher rep ranges (above 10). Individual factors like training experience, muscle fiber composition, and exercise type affect results. Use your calculated 1RM as a starting point and adjust based on experience.

No single formula is universally most accurate. Brzycki and Epley are most commonly used and validated. Brzycki tends to be more accurate for higher rep ranges, while Epley works well for lower reps. Using the average of multiple formulas often provides the best estimate.

Training programs often prescribe weights as percentages of your 1RM: 90-100% for strength (1-3 reps), 75-85% for hypertrophy (6-12 reps), 60-75% for muscular endurance (12+ reps). Use the percentage chart to find appropriate weights for your goals.

Direct 1RM testing every 8-12 weeks is sufficient for most lifters. You can estimate more frequently using submaximal sets. Testing too often increases injury risk and takes recovery time away from training. Track progress through rep PRs at various weights.

These formulas were developed primarily for compound lifts like squat, bench press, and deadlift. They may be less accurate for isolation exercises, machine exercises, or highly technical movements like Olympic lifts. Adjust expectations accordingly.