You have probably noticed that many gym programs tell you to use for example 60 – 80 1RM (Rep Max) weight. The percentage is calculated based on your one repetition maximum of the exercise. In other words if you bench press 100 kg once you have to use 60 – 80 kg weight in the set.
What if I don’t know my one rep max and I don’t have time to test it?
Testing one rep maximums takes time and it’s not always even possible to do by yourself. Anyhow there is a formula which helps you to estimate your one rep max surprisingly accurately. (At least it worked for me really well with almost all the exercises.)
Formula is explained in detail later, but here is the One Rep Max calculator to help you estimate your 1RM.
Formula for estimating 1 rep maximum
| Reps | %1RM |
| 1 | 100 |
| 2 | 95 |
| 3 | 90 |
| 4 | 88 |
| 5 | 86 |
| 6 | 83 |
| 7 | 80 |
| 8 | 78 |
| 9 | 76 |
| 10 | 75 |
| 11 | 72 |
| 12 | 70 |
For example if you managed to do 7 reps with 50 kg then 50 kg is 80 % of your one rep max. So your estimated one rep max is 50 kg / 0,8 = 62,5 kg
If the workout plan says “use 60 % 1 RM weight” do the set with 0,6 * 62,5 kg = 37, 5 kg.
Yayy, math!
