One Rep Max Calculator — Estimate Your 1RM Free (2026)
Free one-rep max calculator. Enter a weight and the reps you hit to estimate your 1RM with the Epley and Brzycki formulas, plus a full %-of-1RM training table.
Your one-rep max is the most weight you could lift for a single rep — the anchor most strength programs are built around. Estimate it safely from a set you've already done, then read your training loads off the percentage table.
How the estimate works
Instead of risking a true single-rep max, you can estimate it from a set you've already completed. Enter the weight and how many clean reps you got, and the calculator works backward to your one-rep max. The fewer the reps, the more accurate the estimate — a set of 3–5 is the sweet spot.
This tool shows two of the most-used formulas: Epley as the headline and Brzycki for comparison. At 1 rep both give the weight you lifted. From 2 to 9 reps Epley reads a little higher, by about 4% at 2 to 5 reps, and at 10 reps the two match. At 11 and 12 reps Brzycki reads higher. The input stops at 12 because estimates from longer sets are less reliable.
Using your training percentages
Most strength programs prescribe loads as a percentage of your 1RM — for example, 5 sets of 5 at 80%. The table above turns your estimated max into concrete weights for every common percentage, so you can plan a session without guessing. Re-test every few weeks; as you get stronger, the whole table shifts up with you.
Formula & sources
Epley formula
At 1 rep the calculator returns the weight you lifted, since a single rep is already your max.
Brzycki formula
w = weight lifted, r = reps completed. Estimates are most accurate for low rep counts (r ≤ 10).
Sources
- Epley B (1985) Poundage Chart. Boyd Epley Workout. Lincoln, NE.
- Brzycki M (1993) Strength testing — predicting a one-rep max from reps-to-fatigue. JOPERD 64(1):88–90.
One rep max FAQ
How accurate is a one-rep max calculator?
Very good when estimated from a low-rep set (1–5 reps), within a few percent for most lifters. Accuracy drops as reps rise, because muscular endurance starts to vary more between people, which is why estimates from sets above ~10 reps are less reliable.
Which one-rep max formula is best?
Use both. Epley and Brzycki are the two most popular, and they give the same answer at 1 rep and at 10 reps. From 2 to 9 reps Epley reads a little higher, up to about 4%, and at 11 or 12 reps Brzycki does. Seeing both gives you a sensible range instead of one number that looks more exact than it is.
Do I need to actually lift my max to find it?
No — that's the point of the estimate. Testing a true 1RM is fatiguing and carries more injury risk. Estimating from a normal working set taken close to failure is safer and accurate enough for programming.
How do I use my 1RM for training?
Strength programs prescribe loads as a percentage of your 1RM. Use the percentage table to set your working weights — e.g. ~80% for sets of 5, ~70% for sets of 10 — and re-estimate every few weeks as you get stronger.