Why use this calculator
Knowing your one-rep max (1RM) is essential for programming strength training. It helps you determine the right weight for any rep range without needing to actually attempt a dangerous maximal lift.
How to use it
Select your preferred unit system, then enter the weight you lifted and how many reps you completed. The calculator estimates your 1RM and shows training percentages in your selected units.
The formula
Epley Formula: 1RM = Weight × (1 + Reps/30). This is one of the most widely-used and validated estimation formulas.
Worked examples
185 lbs for 8 reps (imperial)
Estimated 1RM of ~234 lbs
84 kg for 8 reps (metric)
Estimated 1RM of ~106 kg
When people use it
- Strength training programming
- Progress tracking
- Competition preparation
- Workout planning
Tips
- Most accurate with 1-10 reps
- Use sub-maximal estimates (90-95%) for safety
- Recalculate periodically as you get stronger
- Different exercises may use slightly different percentages
Questions people ask
- How accurate is this estimate?
- The Epley formula is most accurate with 1-10 reps. Accuracy decreases with higher rep counts. Individual variation exists — use it as a starting point and adjust based on your experience.