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A one-rep max (1RM) is the heaviest weight you can lift for a single repetition with good form. Testing it directly is fatiguing and carries injury risk, so lifters commonly estimate it instead from a lighter set taken close to failure.
This calculator uses the Epley formula, one of the most widely used estimation methods in strength training, and also shows common training percentages (70%, 80%, 90% of 1RM) for programming your next sets.
How it works
Enter the weight you lifted and the number of reps you completed with good form. The tool applies the Epley formula to estimate your one-rep max, then calculates 70%, 80%, and 90% of that number for common training zones.
- Enter weight lifted.
- Enter reps completed.
- Click Calculate to see your results.
Examples
Estimating 1RM from a set of 5
Lifting 100kg for 5 reps gives an estimated one-rep max of about 116.7kg.
Who should use it
- Programming training percentages without testing a true 1RM.
- Tracking estimated strength progress over time from working sets.
Industry applications
- Strength training and powerlifting
- Personal training and coaching
Advantages
- Avoids the fatigue and injury risk of testing a true one-rep max directly.
- Includes ready-to-use training percentages alongside the estimate.
Limitations
- Less accurate at very high rep counts.
- Estimate can vary from your true 1RM depending on how close to failure the set was taken.
Common mistakes to avoid
- Estimating from a set that wasn't close to failure, which tends to underestimate true 1RM.
- Relying on estimates from very high rep counts (15+), where the formula becomes less accurate.
Best practices
- Use a set taken close to (but not necessarily at) failure, in the 3-8 rep range, for the most reliable estimate.
Tips
- Recalculate periodically as your working weights increase, since your true 1RM changes as you get stronger.