One-Rep Max Calculator
Estimate your true 1RM from any set. Uses Epley, Brzycki and Lombardi - averaged for accuracy - plus a full training-percentage table.
Training percentages
| % of 1RM | Weight | ~Reps |
|---|
Rep maxes
| Rep max | Weight | % of 1RM |
|---|
How it works
A one-rep max estimator predicts the most you could lift once from a set you actually did. This tool averages three classic formulas:
Epley: 1RM = w · (1 + reps/30)Brzycki: 1RM = w · 36 / (37 − reps)
Lombardi: 1RM = w · reps0.10
Averaging smooths out each formula's bias. The percentage table is then derived from your estimated 1RM so the loads stay self-consistent.
Worked example
Bench 100kg × 5: Epley gives ≈117kg, Brzycki ≈113kg, Lombardi ≈117kg → an averaged 1RM of about 115kg. Your 5×5 working weight at 80% would be ~92kg.
Frequently asked questions
What is a one-rep max (1RM)?
The most weight you can lift for a single full rep of an exercise. It's the reference point most strength programs use to assign loads as a percentage of 1RM.
Which formula is most accurate?
No single formula wins for everyone. Epley and Brzycki are the most widely used; Lombardi behaves differently at higher reps. Reporting each plus an average is more robust than one equation. All are most accurate at 1–5 reps.
Is it safe to test a true 1RM?
Maxing out carries more injury risk and needs a proper warm-up, good technique and ideally a spotter. Estimating from a 3–5 rep set is safer and accurate enough for programming.
How do I use percentages for programming?
Multiply your 1RM by the prescribed percentage. 5×5 at 80% of a 140kg 1RM = 112kg. The table above gives the load and approximate reps for each percentage.
Why do estimates drift at high reps?
The formulas are fitted to low-rep performance. Past ~10–12 reps, endurance and technique vary too much between people for one set to predict a true max well. Use 5 reps or fewer for the best estimate.