What does this tool do?
The One Rep Max (1RM) calculator estimates the maximum weight you could lift for a single repetition based on a weight and rep count you actually performed. It is built for lifters and coaches who want a safe strength estimate for squat, bench press or deadlift without attempting a true max.
How to use it
- Enter your values into the fields.
- The result is calculated instantly.
- Read or copy the result.
Why averaging three formulas is more reliable
Instead of one equation, this tool blends three: Epley, Brzycki and Lombardi. Each behaves slightly differently across rep ranges, so Brzycki tends to be sharper at low reps while Epley holds up better in the mid range. By averaging all three, the calculator smooths out the extremes that any single formula can produce and gives a more balanced 1RM. The individual Epley, Brzycki and Lombardi values are shown beneath the result so you can see the spread for yourself.
Turn percentages into a training plan
The calculator lays out your estimated 1RM from 50% up to 100% in a ready-made table. Most strength programs prescribe sets as a percentage of your max, such as 85-95% for strength, 70-80% for hypertrophy and 50-60% for warm-ups. With this grid you can read the exact load for every set in seconds, with no pen-and-paper math, and switch between kg and lb with a single tap before you start lifting.
Frequently asked questions
Up to how many reps does the estimate stay accurate?
1RM formulas are most accurate in the 1-10 rep range. Above roughly 10-12 reps, muscular endurance starts to dominate and estimates tend to overshoot, so use a set where you reached fatigue around 3-6 reps if you can.
Should I actually try to lift the estimated 1RM?
No, it is an estimate. A real one-rep max attempt should only be done with a proper warm-up, a spotter and solid technique. The point of the calculator is to help you plan your program without taking a risky max attempt.
Do I need separate calculations for squat, bench and deadlift?
Yes. Each lift uses different muscle groups and leverage, so their 1RM values diverge. Enter the weight and reps from your top set of each exercise and calculate them separately.
Is One Rep Max (1RM) free?
Yes. One Rep Max (1RM) and all 300+ tools on MagmaNex are completely free with no signup or account required.
Is my data safe?
Yes. Everything runs locally in your browser. The data you enter is never sent to a server, stored, or shared.
Does it work on mobile?
Yes. One Rep Max (1RM) works on phones, tablets and desktops — no app download needed.
🔒 Privacy: everything runs in your browser, your data is never sent to a server.