Last updated: 4 October 2026
Reviewed by Jordan Morley, FA Level 2 Football Coach
Your one-rep max (1RM) is the maximum weight you can lift for a single repetition with full effort. Testing 1RM directly carries injury risk; instead, coaches use sub-maximal formulas. The Epley formula: 1RM = weight × (1 + reps/30). The Brzycki formula: 1RM = weight × (36 / (37 − reps)). Both are accurate to within 5-10% for sets of 1-10 reps. Sets of more than 10 reps produce less reliable estimates. 1RM is used to set training percentages across strength programmes.
- Epley: weight × (1 + reps/30)
- Brzycki: weight × 36/(37-reps)
- Accurate to ~5-10% within 1-10 rep range
- Used to calculate training percentages
In practice
Several different formulas (Epley, Brzycki, Lander, among others) estimate one-rep max from a submaximal set, and while they broadly agree at moderate rep ranges, their estimates diverge more as rep count increases — most coaches recommend using sets of 10 reps or fewer for the most reliable 1RM estimate, since formulas become progressively less accurate at very high rep counts.
FAQ
Which one-rep max formula is most accurate?
No single formula is universally most accurate — the Epley and Brzycki formulas are among the most widely used, and most agree closely for sets of around 5-8 reps but diverge more at higher rep counts.
Why do 1RM formulas become less accurate at higher reps?
Fatigue and endurance factors increasingly influence performance at higher rep counts in ways that don't scale linearly with pure strength, reducing the formulas' accuracy the further the test set is from a true single maximal effort.