CalcFitLab

One-Rep Max Calculator

Estimate your 1RM from a set, with a % loading table.

Most accurate at 2-10 reps taken near failure.

Estimate · 1RM

114.6 kg

Epley: 116.7 kgBrzycki: 112.5 kg

Percentage of 1RM (based on the average)

% 1RMLoad (kg)Typical reps
100%1151
95%1092
90%1034
85%976
80%928
75%8610
70%8012
65%7415
Reviewed by the CalcFitLab Editorial TeamUpdated 2026-08-01Read our methodology

How the one-rep max calculator works

Your one-rep max (1RM) is the most weight you can lift for a single repetition. Testing a true 1RM is risky, so most lifters estimate it from a set taken close to failure.

This tool shows two published estimates. The Epley formula (1985) is 1RM = weight x (1 + reps/30). The Brzycki formula (1993) is 1RM = weight x 36 / (37 - reps). Both are accurate for sets up to about ten reps and diverge as rep counts climb.

The percentage table below turns your estimated 1RM into working loads. It follows the standard strength-training relationship where roughly 85% of 1RM allows about 6 reps and 75% allows about 10.

  • Estimates are most accurate at 2-10 reps. Above that, error grows quickly.
  • Epley and Brzycki agree closely at low reps and separate as reps rise. Use them as a range, not a single true value.
  • Round working weights to the nearest plate you actually have.

Frequently asked questions

Neither is universally better. They match closely at low reps; Epley tends to read slightly higher at high reps. Using both gives you a sensible range rather than a single point estimate.
Between 2 and 10 reps taken close to failure. Single-rep and very high-rep sets make the estimate less reliable.
Yes. A true 1RM attempt carries higher injury risk, especially without a spotter. Estimating from a moderate set avoids maximal loading while still guiding your training percentages.