One Rep Max Calculator

Calculate your one rep max with Epley, Brzycki, Lombardi, Mayhew and O'Conner formulas. Includes plate loading calculator and percentage tables.

About This Tool

This calculator estimates your one-repetition maximum (1RM) — the maximum weight you can lift for a single repetition. It uses scientifically validated formulas and includes a plate loading calculator to help you set up your barbell efficiently.

Features

  • Five proven 1RM estimation formulas
  • Automatic plate loading calculation per side
  • Percentage tables with training recommendations
  • kg / lbs unit switching with instant conversion
  • Customizable available plate inventory
  • 100% client-side — no data leaves your device

Frequently Asked Questions

What is One Rep Max (1RM)?
One Rep Max is the maximum amount of weight you can lift for a single repetition of a given exercise. It is commonly used to measure strength and program training loads.
How accurate are 1RM formulas?
Accuracy varies by individual and rep range. Formulas are most accurate when calculated from 1-5 reps. Higher rep estimates tend to overpredict 1RM. Use multiple formulas and consider the average.
Which formula should I use?
Epley and Brzycki are the most widely used. Epley tends to be slightly more optimistic at higher reps. Brzycki is conservative. Use the average of multiple formulas for the best estimate.
How do I use the plate calculator?
Enter your target weight and bar weight, select which plates your gym has, and the tool will calculate exactly what to load on each side of the barbell.