1RM (One Rep Max) calculator
Your 1RM (One Rep Max) is the maximum weight you can lift for a single repetition with proper form. It's the benchmark for programming workouts, tracking progress and comparing performance. This calculator estimates your 1RM from your working sets, without having to test your actual max.
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Try for freeWhy knowing your 1RM matters
Most serious training programs use percentages of 1RM to define training loads. For example: 5x5 at 80% 1RM for strength, 3x10 at 65% for hypertrophy. Without knowing your 1RM, you can't program effectively and risk training too light or too heavy.
How to use this calculator
- 1Select or type the exercise name
- 2Enter the weight you lifted
- 3Enter the number of reps completed (2-12 reps)
- 4Choose the unit (kg or lbs)
- 5Check your estimated 1RM and percentage table
Tips for an accurate 1RM
- •Use a set of 3-5 reps for a more accurate estimate
- •Beyond 10 reps, the margin of error increases significantly
- •Make sure your form is correct on the set used
- •The calculated 1RM is an estimate — test carefully with a spotter
- •Retest your 1RM every 4-8 weeks to adjust your program
Frequently asked questions
For sets of 1-6 reps, the Brzycki formula is generally most accurate. For longer sets (6-12 reps), Epley gives better results. This calculator averages all three formulas for an optimal estimate.
Testing your real 1RM carries injury risk, especially without experience. That's why this calculator is useful: it estimates your 1RM from lighter, safer sets.
They're most accurate for compound movements (squat, bench, deadlift). For isolation exercises, the margin of error is larger.
The table shows the weight to use for each rep count. For example, for hypertrophy (8-12 reps), work at 65-75% of your 1RM.