Tools/1RM calculator
One-rep max calculator
In short
Enter the weight and the reps of a hard set. The calculator estimates the heaviest weight you could lift once, with the Epley formula: weight × (1 + reps ÷ 30). It is most reliable for sets of up to about 10 reps.
Epley formula: weight × (1 + reps ÷ 30). Fairly reliable up to about 10 reps.
In the Mitta app
- It learns from youMitta starts from this formula. With Pro, it then adjusts to what you log.
- Every number explainedTap “Why?” on any target to see the sum behind it.
- Free to startIn the web app for invited testers.
Weight for 2 to 12 reps
| Reps | Weight | Share of your max |
|---|---|---|
| 2 | – | 94% |
| 3 | – | 91% |
| 4 | – | 88% |
| 5 | – | 86% |
| 6 | – | 83% |
| 8 | – | 79% |
| 10 | – | 75% |
| 12 | – | 71% |
How the estimate works
The Epley formula assumes that every rep you add takes about 3.3% off the weight you can lift. So 100 kg for 8 reps gives 100 × (1 + 8 ÷ 30) ≈ 127 kg.
The estimate is best from a set taken close to failure. If you stopped with reps left in the tank, add those reps before you calculate, or the estimate will be too low. Mitta does this for you when you log how many reps you had left.
What to use it for
You do not need to test a true max to train well. An estimate is enough to:
- pick a starting weight for a new rep range;
- see whether you are getting stronger when your sets change from week to week;
- compare lifts done for different reps.
Read more in What is estimated 1RM, and how accurate is it?
Questions about the
1rm calculator
How accurate is a 1RM calculator?
For sets of about 10 reps or fewer, taken close to failure, the estimate is usually close. With higher reps the error grows, because people differ a lot in how many reps they can do at a given share of their max.
Which formula does this calculator use?
The Epley formula: weight × (1 + reps ÷ 30). Mitta uses the same formula in the app for estimated 1RM and records.
Should I test my real one-rep max?
Not unless you compete or want to. An estimate from a hard set of 3 to 8 reps tells you almost as much, with less risk and less fatigue.
What weight should I use for 5 reps?
Enter a recent hard set, then read the table below the result. It shows the estimated weight for 2 to 12 reps.