One Rep Max Calculator

Your one rep max is the maximum amount of weight you can lift for a single repetition with proper form. It is the gold standard for measuring absolute strength and is used to program training percentages for strength, hypertrophy, and endurance work.

Estimation formulas are most accurate with rep counts between 1 and 10. Beyond 10 reps, accuracy decreases because fatigue, technique, and muscular endurance become greater factors. For the most reliable estimate, use a weight you can lift for 3-5 reps. This calculator averages three validated formulas (Epley, Brzycki, Lombardi) to reduce individual formula bias.

Epley (1985) uses a linear model: weight x (1 + reps/30). Brzycki (1993) uses an inverse model: weight x 36/(37-reps). Lombardi uses an exponential model: weight x reps^0.1. Epley tends to predict slightly higher at high rep ranges, Brzycki is more conservative, and Lombardi falls in between. Averaging all three gives the most balanced estimate.

True 1RM testing carries injury risk and should only be attempted after proper warm-up, with a spotter, and by lifters with solid technique. For most training purposes, estimating your 1RM from a submaximal set of 3-5 reps is safer and nearly as accurate. Save true max attempts for competition or periodic testing under controlled conditions.

Retest every 8-12 weeks to track progress and adjust your training loads. Beginners may progress faster and can retest every 4-6 weeks. Between tests, use the percentage table to program your training weights based on your most recent estimated 1RM.

The strength standards in this calculator are body-weight multipliers derived from research by Lon Kilgore, ExRx normative data, and Symmetric Strength community data. They represent approximate benchmarks for untrained (beginner), recreationally trained (intermediate), competitively trained (advanced), and elite-level lifters. Standards vary by body-weight class and training age.