Epley vs. Brzycki: Which One-Rep Max Formula Should You Use?
October 21, 2026
All one-rep max formulas estimate the heaviest weight you could lift once based on a lighter set to near failure. They agree closely at low reps and diverge as reps climb. For a set of 100 kg for 5 reps, Epley gives 116.7 kg, Brzycki 112.5 kg, O'Conner 112.5 kg, and Lombardi 117.5 kg. Use a set of 3 to 6 reps for the most reliable result.
Skip the math and get your answer instantly:
Open the One-Rep Max Calculator →The Formulas
Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki: 1RM = weight × 36 ÷ (37 − reps). O'Conner: weight × (1 + 0.025 × reps). Lombardi: weight × reps^0.10.
Epley and Lombardi tend to give higher estimates at moderate reps, while Brzycki and O'Conner give slightly lower ones. None is universally correct, since individual strength endurance varies.
| Formula | 100 kg × 5 reps | 100 kg × 10 reps |
|---|---|---|
| Epley | 116.7 kg | 133.3 kg |
| Brzycki | 112.5 kg | 133.3 kg |
| O'Conner | 112.5 kg | 125.0 kg |
| Lombardi | 117.5 kg | 125.9 kg |
Why Higher Reps Are Less Reliable
The relationship between reps and percentage of 1RM varies a lot between people and between lifts. One person might manage 15 reps at 70% of their max, another only 8. As reps rise, small differences in muscular endurance produce large errors in the estimate.
Brzycki also breaks down mathematically near 37 reps, where the denominator reaches zero. Treat anything above about 10 reps as a rough guess.
Using Your Estimate Safely
Use estimated 1RM to set training percentages, not to attempt a true max without a spotter. Choose a set that ends close to failure but with good form, and apply the same formula over time so you can compare progress.
If your estimate rises from 112 kg to 120 kg over a training block, the trend matters more than which formula you chose.
Frequently Asked Questions
Which 1RM formula is most accurate?
No formula is best for everyone. Epley and Brzycki are both widely used and agree within a few percent at 3 to 6 reps.
How many reps should I use to estimate my 1RM?
Sets of 3 to 6 reps to near failure give the most reliable estimates. Beyond 10 reps, accuracy declines.
Is it safe to test a true 1RM?
It carries injury risk, particularly without a spotter or safety bars. Estimating from a submaximal set is a safer alternative.
Does the formula work for all exercises?
It works best for big compound lifts. Isolation exercises and machine lifts may follow different rep-to-load patterns.