One Rep Max Calculator
Estimate your one-rep max (1RM) from a sub-maximal lift using the Epley, Brzycki, Lombardi or O'Conner formulas. Useful for programming strength training.
How to use the One Rep Max Calculator
- Enter your inputs into the One Rep Max Calculator above.
- Results update instantly as you type — no submit button needed.
- Adjust any value to see how the result changes in real time.
The 1RM formulas
Epley: 1RM = W × (1 + reps/30) · · · Brzycki: 1RM = W × 36 / (37 − reps)
W is the weight lifted, reps is the number of clean reps completed. Each formula is most accurate in the 1–10 rep range; beyond 10 reps, estimates diverge significantly.
Worked example
8 reps with 225 lb on bench press by Epley: 1RM = 225 × (1 + 8/30) = 225 × 1.267 = 285 lb. Brzycki: 225 × 36/29 = 279 lb. Average estimate ≈ 282 lb.
Frequently asked questions
When should I test my 1RM directly?
Powerlifters and competitive lifters do periodically. For most trainees, estimating from a 3–5 rep set is safer and produces the same training value.
Why do the formulas disagree?
Each was derived from different populations and lifts. Epley is generally accurate in the 5–8 rep range; Brzycki is closer in the 2–5 range. Test a few against your actual 1RM to find which fits your lifts.
How do I program training using 1RM?
Common splits: strength work at 80–95% 1RM for 1–6 reps; hypertrophy at 65–80% for 6–12 reps; endurance at 50–65% for 12+ reps. Most programs cycle between these intensities.