How to Estimate Your One Rep Max
You can estimate a one rep max from a set you already did. Here are the Epley and Brzycki formulas and how to use them safely.
Your one rep max, or 1RM, is the heaviest weight you can lift once with proper technique. It is a handy reference for programming, since many plans set loads as a percentage of it. Testing a true 1RM is demanding and carries some risk, so most people estimate it instead from a set they can already do.
Epley and Brzycki
Two formulas dominate. The Epley formula is weight times (1 plus reps divided by 30). The Brzycki formula is weight divided by (1.0278 minus 0.0278 times reps). Both take the weight you lifted and the number of clean reps you completed, then project what a single max would be.
- Epley: 1RM = weight x (1 + reps / 30).
- Brzycki: 1RM = weight / (1.0278 - 0.0278 x reps).
- Use a set taken close to failure for a fair estimate.
- Results converge at low reps and diverge at high reps.
Say you lift 100 kg for 5 clean reps. Epley gives 100 x (1 + 5/30) which is about 117 kg. Brzycki gives 100 / (1.0278 minus 0.139) which is about 112 kg. Both land in the same neighbourhood, which is exactly what you want from an estimate.
Using the number well
Accuracy drops as reps climb, because a set of 20 reps involves endurance as much as strength. Keep test sets in the 3 to 8 rep range for the cleanest estimate, and re-estimate every few weeks as you get stronger.
Used sensibly, an estimated 1RM lets you set training loads without ever attempting a true max. Recalculate as you progress and let the number guide your percentages.