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Understanding Your One Rep Max
Everything you need to know about 1RM testing, formulas, and training applications.
What is a One Rep Max?
A one rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. It serves as the benchmark for programming training loads across all rep ranges.
Rather than attempting a true max lift (which carries injury risk), these validated formulas estimate your 1RM from submaximal sets -- giving you the data without the danger.
The Formulas We Use
- Brzycki (1993): Most accurate for 2-10 reps. Weight / (1.0278 - 0.0278 x reps)
- Epley (1985): Good across all rep ranges. Weight x (1 + reps/30)
- Lombardi: Weight x reps^0.10. Works well for higher rep ranges.
We average all three for the most reliable estimate. Accuracy is best with sets of 2-10 reps.
Training Zone Guide
- Strength (85-100%): 1-5 reps. Maximal neural recruitment, builds absolute strength.
- Hypertrophy (65-84%): 6-12 reps. Optimal mechanical tension for muscle growth.
- Endurance (50-64%): 13-20+ reps. Builds muscular endurance and work capacity.
1RM Testing Safety: Always warm up thoroughly before heavy lifts. Use a spotter for barbell movements. If you have not tested your max before, start with a weight you can confidently lift for 3-5 reps and use this calculator instead of attempting a true max. Never sacrifice form for a heavier weight.
How to Use Your 1RM for Programming
Once you know your estimated 1RM, you can program your training using percentage-based loading. This is the foundation of periodization -- systematically varying intensity and volume to drive adaptation.
RPE and Reps in Reserve
RPE (Rate of Perceived Exertion) adds a subjective adjustment to your estimate. An RPE of 10 means you gave maximum effort with nothing left. An RPE of 8 means you had about 2 reps in reserve. Our calculator adjusts the estimated 1RM based on your reported RPE to account for days where you are not at full capacity.
When to Retest
Retest your 1RM every 4-8 weeks, or whenever your training weights feel noticeably easier than prescribed. Progressive overload is the key to strength gains -- your percentages should evolve as you get stronger.