One Rep Max Calculator
Estimate your one-rep max (1RM) from a set you lifted, using the Epley and Brzycki formulas, plus a full percentage table for programming your lifts. Runs in your browser.
Part of 💪 Free Health & Fitness Calculators
Estimates only — attempting a true max lift can be risky. Warm up, use a spotter, and train within your limits.
✔ 100% Free✔ No Signup✔ No Watermark✔ Unlimited Use
Estimate Your One Rep Max
This free one rep max calculator estimates the most weight you could lift for a single rep (your 1RM) from a set you have already done, without you having to attempt a risky max lift. Enter the weight and the number of reps, and it averages the trusted Epley and Brzycki formulas for a solid estimate.
It also gives you a full percentage table, showing the weight for 60% to 100% of your 1RM, which is exactly what strength programs use to prescribe your working sets. Everything runs in your browser, in kg or lb.
How to Use the One Rep Max Calculator
- 1Enter the weight you lifted and its unit.
- 2Enter how many reps you completed.
- 3Read your estimated 1RM.
- 4Use the percentage table to plan your working sets.
Why Use MakeToolz's One Rep Max Calculator?
Two proven formulas
Averages the Epley and Brzycki equations for a balanced estimate.
Full percentage table
Shows the weight for 60% to 100% of your 1RM for programming.
Safe estimate
Get your max from a normal set instead of attempting a risky single.
kg or lb
Works in either unit with one click.
100% in your browser
No signup and nothing uploaded; it all runs locally.
Free and instant
Results update as you change weight or reps.
Why Estimate Your 1RM
Your one-rep max is the foundation of most strength programs, but actually testing it is risky and tiring, and you cannot do it every week. Estimating it from a normal working set gives you the number without the danger. The math works because there is a predictable relationship between how much you lift and how many times you can lift it, at least up to about ten reps. This tool averages two of the most trusted formulas, Epley and Brzycki, so a quirk in either one has less effect on your estimate.
The percentage table then turns that estimate into practical loads for your program. It runs entirely in your browser, with no signup and no limit.
Getting the Best Estimate
- Use a heavy set: a set of 3 to 6 reps estimates better than a set of 15.
- Go close to failure: the formula assumes the reps were genuinely hard.
- Warm up first: a fresh, warm set gives a truer number.
- Re-check periodically: recalculate as you get stronger.
Training Percentages
| % of 1RM | Typical reps | Common use |
|---|---|---|
| 90 to 100% | 1 to 4 | Max strength |
| 75 to 85% | 6 to 10 | Strength and size |
| 60 to 70% | 12 to 20 | Endurance, technique |
People Also Ask
What is a one rep max?
It is the maximum weight you can lift for a single repetition of an exercise. This tool estimates it from a set you already completed.
Which 1RM formula is best?
Epley and Brzycki are both widely used and give similar results at low reps. This calculator averages them so you get a balanced estimate.
How do I use 1RM percentages?
Multiply your 1RM by the percentage your program calls for. The table above does this for you, from 60% up to 100%.
Is one rep max the same for every exercise?
No. Your 1RM is specific to each lift, so calculate it separately for the squat, bench, deadlift and other movements.
Is the one rep max calculator free?
Yes, completely free with no signup and no limits. Everything runs in your browser.
Does it store my lifts?
No. Everything is calculated locally in your browser and nothing is uploaded or saved.