What this tool does
1RM Calculator helps you estimate your one rep max, the heaviest weight you could lift for a single repetition, without having to actually lift it. Enter the weight and reps from a recent set, and the calculator does the rest in an instant.
Along with your estimated max, you get:
- Results from 7 well-known formulas (Epley, Brzycki, Lombardi, Lander, O'Conner, Mayhew and Wathan), averaged into one balanced number.
- A strength level for the bench press, squat, deadlift and overhead press, based on your bodyweight.
- A training percentage chart from 50% to 100% of your max, so you know exactly what to load on the bar.
- Support for both kg and lbs, plus light and dark mode.
Why we built it
Most strength programs tell you to lift a percentage of your one rep max, but testing a true max is tiring, takes time, and isn't always safe, especially for newer lifters. We wanted a calculator that is quick to use on a phone between sets, explains its numbers clearly, and doesn't bury the result under clutter.
How it works
Each formula was developed by coaches and researchers who compared how many reps people could do with how much they could lift once. Because every formula has a small bias, we show all seven and use their average as your main result. You can read the formulas and how accurate they are in the guide on the calculator page.
All calculations happen right in your browser. The numbers you type are never sent to us or stored on a server.
Who it's for
Whether you're a beginner planning your first program, a powerlifter preparing for a meet, or a coach writing plans for clients, the calculator gives you a reliable starting point in seconds.
Remember: results are estimates, not medical or professional advice. Always lift with good form and listen to your body. See our Terms of Use for details.
Get in touch
Found a bug, have an idea, or just want to say hello? We'd love to hear from you. Visit the contact page.