Rep Max Converter
Enter any weight and rep count to estimate your max for every rep range from 1 to 12.
| Rep max | Weight | % of 1RM | Zone |
|---|
Converting Between Rep Ranges
Strength programs regularly move between rep ranges across training phases. A hypertrophy block might use sets of 8-10 reps, while a strength block uses 3-5 reps, and a peaking phase uses 1-3 reps. Without a rep max converter, you would need to guess your starting weight each time you switch phases - which wastes several sessions of suboptimal loading while you dial in the right weight.
The Epley formula provides reliable estimates for sets of 1-8 reps performed close to failure. For sets above 10 reps, endurance factors become dominant and the formula becomes less predictive. Use the converted values as a starting point, then adjust based on how the weight actually feels. A good rule of thumb: if your first set felt easy, add 2.5-5%, if it was borderline too hard, reduce by the same margin.
Frequently Asked Questions
What is a rep max converter?
A rep max converter estimates your maximum for any rep count from a known performance at another rep count. For example, if you know your 5RM, it estimates your 1RM, 3RM, 8RM, and so on - all from that single data point.
Which formula does this use?
This calculator uses the Epley formula (1RM = weight x (1 + reps/30)) as its basis, then derives other rep maxes from the estimated 1RM. Results are most accurate for the 2-8 rep range and become less reliable above 12 reps.
Is a 5RM or 3RM more accurate for estimating 1RM?
Generally, a lower rep set gives a more accurate 1RM estimate. A 3RM is more reliable than a 5RM, and a 5RM is more reliable than an 8RM. As rep count increases, individual differences in strength endurance cause the estimates to diverge from reality.
Why does my actual 8RM differ from the estimated one?
The formulas assume average strength endurance. Some lifters are better at higher reps (higher slow-twitch muscle fiber proportion), others fatigue faster and are better at low rep work. These individual differences mean estimates are guidelines, not precise predictions.
How should I use these numbers in my training?
Use the converted rep maxes to set target weights when switching rep ranges in your program. For example, if you are moving from a 5-rep phase to an 8-rep phase, the estimated 8RM gives you a starting point for your working weight.