One Rep Max Calculator

Estimate your one-rep max for any lift using the Epley and Brzycki formulas.

About this calculator

Your one-rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. It is a key metric for structuring training programs, since most percentage-based programs prescribe loads as a percentage of your 1RM. This calculator uses two validated formulas (Epley and Brzycki) to estimate your 1RM from a submaximal lift, so you do not need to actually attempt a max-effort single. Both formulas are most accurate when you input a weight you lifted for 2-10 reps. Beyond 10 reps, the estimates become less reliable because muscular endurance starts influencing the result more than maximal strength. The calculator also shows training load percentages, helping you pick the right weight for different rep ranges and training goals.

Frequently asked questions

Which formula is more accurate, Epley or Brzycki?

Both are validated and produce similar results for low rep ranges (2-6 reps). Epley tends to estimate slightly higher at higher rep ranges. Most coaches use whichever is standard in their sport. If results differ, use the lower estimate for safety.

How often should I test or update my 1RM?

Recalculate every 4-8 weeks, or whenever you hit a new rep PR at a given weight. There is rarely a reason to test an actual 1RM unless you compete in powerlifting or weightlifting. Estimated 1RM from a strong set of 3-5 reps is safer and nearly as useful.

What rep range should I train in?

It depends on your goal. For strength, train at 80-90% of 1RM (3-6 reps). For muscle growth, 65-80% (6-12 reps) is most efficient. For muscular endurance, use 50-65% (12-20 reps). Most programs include a mix of all three.

These numbers are a starting point. If you want help turning them into a plan you'll actually stick to, I do 1-on-1 coaching.

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