Calculate your one rep max (1RM) using multiple proven formulas. Estimate your maximum lift based on weight and reps.
| Formula | 1RM |
|---|
| Percentage | Weight | Training Goal |
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Testing an actual one-rep max (the heaviest weight you can lift for a single complete repetition) carries real injury risk, especially for beginners or anyone without a spotter, which is exactly why estimation formulas like Epley or Brzycki exist - they calculate an estimated 1RM based on a lighter weight lifted for multiple reps, using the well-established relationship between rep count and percentage of true maximum strength. This lets lifters program training percentages (like "work at 80% of 1RM") without needing to actually max out regularly.
Strength training programs are frequently built around percentages of 1RM, since training at different percentage ranges targets different adaptations - lower reps at higher percentages build maximal strength, while higher reps at lower percentages build more muscular endurance and hypertrophy.
These formulas are most accurate when based on sets of roughly 10 reps or fewer - estimating 1RM from a set of 20+ reps introduces more error, since the relationship between rep count and strength percentage becomes less linear and less reliable at very high rep ranges.
One rep max is the maximum weight you can lift for a single repetition of an exercise with proper form. It's a standard measure of strength used in training programs and progress tracking.
1RM calculators provide estimates, not exact values. Accuracy varies based on the exercise, experience level, and how close the test set is to failure. For beginners, estimates may be less accurate. Actual testing is more precise.
Different formulas were developed using different populations and methodologies. Epley is popular for bodybuilding, Brzycki for general fitness. Comparing multiple formulas gives you a range to work with.
Testing actual 1RM carries injury risk and requires proper warm-up and spotting. For most people, estimating from submaximal sets is safer. Only test 1RM if you're experienced and have proper supervision.
Training percentages help structure your workouts: 85-95% for strength, 70-85% for hypertrophy, 60-75% for endurance. Use your 1RM to calculate these percentages and plan your training accordingly.
Testing a true 1RM carries real injury risk, especially without a spotter, so estimation formulas based on lighter, higher-rep sets are generally safer.
They're reasonably accurate for sets of about 10 reps or fewer, but become less reliable when estimated from very high-rep sets.
Different percentage ranges target different training adaptations - lower reps at higher percentages build maximal strength, while higher reps at lower percentages build endurance.
