One Rep Max Calculator
Estimate your one-rep max from weight and reps
Estimated one-rep max
Epley
Brzycki
Percentage of 1RM (Epley)
| % of 1RM | Weight | Plate-rounded |
|---|
How to Use
- Choose your units — Toggle between kilograms and pounds. The default follows the page language, and your entered weight converts automatically when you switch.
- Enter the weight you lifted — Any working weight you can lift for a clean set, for example 100 kg.
- Enter the reps performed — A whole number from 1 to 12. If you lifted the weight once, that weight already is your 1RM.
- Read your estimates — The Epley and Brzycki estimates appear side by side, followed by a percentage table (100%–55%) with exact and plate-rounded loads for programming.
Features
- Two proven formulas — Epley and Brzycki estimates shown side by side, so you can see the spread instead of a single black-box number.
- Percentage table — Loads from 100% down to 55% of your estimated 1RM for percentage-based programs.
- Plate-rounded loads — Every table row also shows the nearest loadable weight (2.5 kg or 5 lb steps), ready to put on the bar.
- kg/lb toggle — Locale-aware default unit with one-click switching and automatic conversion.
- 100% client-side privacy — All calculations run in your browser; nothing you enter leaves your device.
Use Cases
- Program planning: Computing training percentages for a 5/3/1, Texas method, or any percentage-based strength program.
- Meet preparation: Estimating openers and attempts for a powerlifting meet without testing a true max in training.
- Progress tracking: Re-estimating your 1RM from rep PRs (e.g. a new 5RM) between max-out cycles.
- Safe estimation: Getting a max figure for beginners who should avoid true one-rep attempts.
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Frequently Asked Questions
What is a one-rep max (1RM)?
Your one-rep max is the maximum weight you can lift for a single full repetition of an exercise with proper form. It is the standard measure of strength and the reference point for percentage-based training programs, which prescribe loads like 80% of 1RM for a given day.
Epley vs Brzycki — which estimate should I use?
Both are well-established formulas and usually agree within a few percent in the 1–12 rep range. Epley (weight × (1 + reps/30)) tends to read slightly higher at higher rep counts; Brzycki (weight × 36 / (37 − reps)) is often a touch more conservative. Treat them as two estimates of the same number — many coaches simply average them or use whichever matches their gym experience.
Why is the rep count limited to 12?
1RM formulas are extrapolations, and their error grows rapidly with reps. Beyond about 12 reps the set measures muscular endurance more than maximal strength, and the same weight can map to wildly different 1RM estimates depending on the lifter. If you can do more than 12 reps, add weight until the set lands in the 1–12 range, then re-enter it.
What does the plate-rounded column mean?
The percentage table shows the exact load for each percent of your estimated 1RM, plus a practical value rounded to the nearest loadable increment — 2.5 kg or 5 lb, matching the smallest plates in most gyms. Barbells can only be loaded in plate-sized steps, so the rounded column is the weight you can actually put on the bar.
How accurate is an estimated 1RM?
It is an estimate, not a measurement. Low-rep sets (3–5 reps) give the most reliable results, typically within a few percent of a true max attempt. Accuracy drops with higher reps, poor rep quality, or exercises where technique breaks down under fatigue. Use the estimate to plan training loads, and confirm with a real max attempt only with a spotter.