One Rep Max Calculator
| % of 1RM | Weight | Goal |
|---|---|---|
| 95% | 0 | Strength (1-3 Reps) |
| 85% | 0 | Power (3-5 Reps) |
| 70% | 0 | Hypertrophy (8-12 Reps) |
| 50% | 0 | Endurance (15+ Reps) |
What is a One Rep Max?
Your One Rep Max (1RM) is the theoretical maximum amount of weight you can lift for a single repetition with proper form. It is the gold standard measurement for strength athletes, powerlifters, and bodybuilders.
However, testing your true 1RM in the gym is dangerous. Attempting to lift a heavy weight you have never handled before creates a high risk of injury.
That is why smart athletes use a 1RM Calculator. By lifting a lighter weight for more reps (e.g., 5 reps), you can use mathematics to predict your max strength safely.
The Math: Epley vs. Brzycki
Our calculator uses two different industry-standard formulas to give you the best estimate:
- Brzycki Formula: Generally considered the most accurate for lower rep ranges (1-10 reps).
- Epley Formula: Tends to be slightly more accurate for higher rep ranges (10+ reps).
How to Use Your Training Percentages
Once you know your 1RM, you shouldn't just try to lift it every day. You should use the Training Zones provided in the results table to structure your workouts.
1. Strength (85% - 95%)
If you want to get stronger, you need to lift heavy. Perform sets of 1 to 5 reps at this percentage. This teaches your nervous system to recruit maximum muscle fibers.
2. Hypertrophy (65% - 80%)
This is the "Bodybuilding Zone." Lifting moderately heavy weight for 8 to 12 reps creates the best stimulus for muscle size growth.
3. Endurance (50% - 60%)
Lifting lighter weights for 15+ reps improves muscular stamina and cardiovascular health, but provides minimal size or strength gains.
Important Safety Warning
This calculator provides an estimate. Actual performance varies daily based on sleep, nutrition, and stress. Never attempt a maximal lift without a spotter.