# How do I calculate my E1RM (estimated one rep max)?

### Published at: September 1, 2024

Understanding your estimated 1-rep max (e1RM) is essential for effective strength training. The e1RM tells you how much weight you can theoretically lift for one rep, guiding your workout intensity and helping you set realistic goals.

There are different exercise science formulae to estimate a one rep max. For those of you who love math:

- Brzycki Formula: 1RM = Weight / (1.0278 - (0.0278 x Reps))
- Epley Formula: 1RM = Weight x (1 + (0.0333 x Reps))
- Lombardi Formula: 1RM = Weight x (Reps^0.10)
- Mayhew Formula: 1RM = (100 x Weight) / (52.2 + (41.9 x e^(-0.055 x Reps)))
- O'Conner Formula: 1RM = Weight x (1 + (0.025 x Reps))
- Wathan Formula: 1RM = (100 x Weight) / (48.8 + (53.8 x e^(-0.075 x Reps)))

These are outlined on this Wikipedia page: https://en.wikipedia.org/wiki/One-repetition_maximum

Existing one-rep max calculators are usually ambiguous and hide the algorithm being used. This is why we created the Strength Journeys One Rep Max Calculator. You can see multiple formulae in one calculator and choose the one based on the result you are looking for - it's science!