What is a one rep max (1RM)?

Your one rep max is the maximum weight you can lift for a single repetition with proper form. It is the standard measure of maximal strength and is used to calculate training loads as percentages.

Is this one rep max calculator completely free?

Yes. No registration, no account, and no payment required.

Do I need an account to use this calculator?

Enter your weight and reps. Your 1RM and training table appear immediately.

Which rep range gives the most accurate 1RM estimate?

Sets of 3–5 reps give the most accurate estimates. As rep counts increase above 8–10, endurance factors influence performance and the formulas become less reliable.

One rep max calculator

One rep max calculator is a health tool that estimates your maximal single-rep lift from a submaximal weight and rep count. It applies the Epley and Brzycki formulas side by side, averages the two estimates, and generates a full 60%–100% training percentage table. The tool runs in your browser.

Exercise

Weight lifted (kg)

Reps performed (1–12)

Dedicated pages

Lift-specific one rep max calculators.

Bench press one rep max calculator

Calculate your bench press one rep max using the Epley and Brzycki formulas. Get a full percentage table for programming. Free, in-browser.

Squat one rep max calculator

Calculate your squat one rep max using the Epley and Brzycki formulas. Full percentage table included. Free, in-browser.

Deadlift one rep max calculator

Calculate your deadlift one rep max using the Epley and Brzycki formulas. Includes a training percentage table. Free, in-browser.

How to calculate your one rep max

Select your exercise, bench press, squat, or deadlift.
Enter the weight you lifted and the number of reps performed (1–12).
Your estimated 1RM appears alongside both Epley and Brzycki formula results.
Use the training percentage table to set your working weights for each intensity zone.

Common uses

Setting training percentages for a powerlifting or strength programme
Tracking strength progress without attempting an actual maximum effort, alongside a body fat calculator for a full picture of progress
Comparing relative strength across different bodyweights and lifts, using a lean body mass calculator for strength-to-muscle ratios

Technical specification

Algorithm or formula: Epley formula 1RM = w * (1 + r/30) (Boyd Epley, 1985) and Brzycki formula 1RM = w * 36/(37-r) (Matt Brzycki, 1993), where w is the weight lifted and r is the rep count. The displayed estimate is the average of the two.
Browser API or library: Pure JavaScript arithmetic; no external library.
Input limits: Weight 1–2,000 (lb or kg). Reps 1–12 (formula accuracy degrades above this range).
Output: Estimated 1RM from each formula, plus a training percentage table from 60% to 100% in 5% steps showing the working weight and a target rep range for each intensity.
Known limitations: Formula-based estimate, not a substitute for an actual tested 1RM. Accuracy decreases as rep count increases (most accurate in the 3–5 rep range).

Frequently asked questions

What is a one rep max (1RM)?: Your one rep max is the maximum weight you can lift for a single repetition with proper form. It is the standard measure of maximal strength and is used to calculate training loads as percentages.
Is this one rep max calculator completely free?: Yes. No registration, no account, and no payment required.
Do I need an account to use this calculator?: Enter your weight and reps. Your 1RM and training table appear immediately.
Which rep range gives the most accurate 1RM estimate?: Sets of 3–5 reps give the most accurate estimates. As rep counts increase above 8–10, endurance factors influence performance and the formulas become less reliable.

Reviewed and tested May 25, 2026.