Why Estimate Your 1RM?
Your one-rep max (1RM) is the foundation of evidence-based strength programming. Knowing it lets you train at precise percentages of your maximum — the method used by elite powerlifters, Olympic weightlifters, and strength coaches worldwide.
Directly testing your 1RM every session is impractical and risky. Submaximal prediction formulas let you estimate it from a set of 3–7 reps at a challenging but manageable weight — safer, faster, and repeatable.
BarbellMax averages three independently validated formulas to give you the most reliable estimate possible.
The Three Formulas
Epley Formula Best: 6–10 reps
1RM = W × (1 + R / 30)
Developed by Boyd Epley at the University of Nebraska in 1985 and later adopted as a standard by the National Strength and Conditioning Association (NSCA). The most widely cited 1RM prediction formula in strength research. Performs slightly better at moderate-to-higher rep ranges.
Brzycki Formula Best: 1–5 reps
1RM = W × (36 / (37 − R))
Published by Matt Brzycki in the Journal of Physical Education, Recreation & Dance (1993). Validated specifically for lower rep ranges where strength expression is more direct. More conservative than Epley and preferred when testing heavy, low-rep sets.
Wathan Formula Best: 5–10 reps
1RM = (100 × W) / (48.8 + 53.8 × e^(−0.075 × R))
Published by Dan Wathan in the NSCA's Essentials of Strength Training and Conditioning (1994). Uses an exponential decay model that more naturally reflects how fatigue accumulates across reps. Considered one of the more accurate formulas across a broad range of rep counts.
Why BarbellMax Averages All Three
Each formula has a different strength depending on your rep range. Rather than forcing you to pick one, BarbellMax averages all three enabled formulas. Research by Reynolds et al. (2006) found that combining multiple validated equations reduces individual formula error and produces more stable estimates across varying rep ranges and training backgrounds.
Accuracy & Limitations
General accuracy: These formulas are typically accurate within 5–10% for trained individuals when testing with 3–7 reps at a weight near your true limit. Accuracy decreases at higher rep ranges (above 10 reps) and for beginners, whose neuromuscular efficiency differs from trained lifters.
Deadlift note: LeSuer et al. (1997) found that all standard 1RM equations significantly underestimate the deadlift — despite achieving very high correlations (r > 0.95) for bench press and squat. This is attributed to the deadlift's unique demands: grip fatigue, inertia from a dead stop, and posterior chain loading patterns that differ from other compound lifts. BarbellMax flags this with a disclaimer on deadlift estimates. Treat your deadlift 1RM as a conservative floor — your actual max is likely slightly higher.
Results also vary based on fatigue, sleep, nutrition, and individual physiology. Use your estimate as a training guide, not an absolute number.
Research Citations
1
Epley, B. (1985). Poundage chart. Boyd Epley Workout. Lincoln, NE.
Adopted by the NSCA as the standard 1RM prediction formula.
Source of the Epley formula; the most widely cited equation in strength training literature.
2
Brzycki, M. (1993). Strength testing: Predicting a one-rep max from reps to fatigue.
Journal of Physical Education, Recreation & Dance, 64(1), 88–90.
Validated for lower rep ranges (1–5). More conservative estimate, preferred for heavy strength work.
3
Wathan, D. (1994). Load assignment. In T.R. Baechle (Ed.), Essentials of Strength Training and Conditioning (pp. 435–446).
NSCA / Human Kinetics.
Exponential decay model considered one of the more accurate formulas across a wide range of rep counts.
4
Reynolds, J.M., Gordon, T.J., & Robergs, R.A. (2006). Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry.
Journal of Strength and Conditioning Research, 20(3), 584–592.
Found 5RM data yields the highest prediction accuracy. Validated the 10-rep ceiling recommendation beyond which accuracy drops significantly.
5
LeSuer, D.A., et al. (1997). The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift.
Journal of Strength and Conditioning Research, 11(4), 211–213.
Key finding: all equations significantly underestimate the deadlift despite high correlations (r > 0.95) for bench press and squat. Basis for BarbellMax's deadlift disclaimer.
6
Macarilla, C.T., et al. (2022). Accuracy of predicting one-repetition maximum from submaximal velocity in the barbell back squat and bench press.
PMC / Sciendo.
Supports 5-rep submaximal testing as optimal. Confirmed traditional formula-based methods remain valid and reliable compared to newer velocity-based alternatives.