One Rep Max Calculator
Calculate lift strength estimates
About the One Rep Max Calculator
Your one-rep max — the most weight you can lift for a single repetition — is the benchmark strength training programs are built around, but testing it directly is risky and tiring. This calculator estimates it from a lighter set you have already done, using the weight lifted and the number of reps.
Lifters use it to set training percentages, track progress without maxing out, and program their next cycle. It computes two well-known estimates side by side — the Epley and Brzycki formulas — so you can see how they compare on the same lift rather than trusting a single number.
How to Use the One Rep Max Calculator
- Enter the weight you lifted for the set.
- Enter the number of reps you completed with that weight.
- Read the Epley estimated one-rep max, shown prominently.
- Compare it against the Brzycki estimate shown alongside, and Copy the result.
Why Use ToolForge’s One Rep Max Calculator
- It calculates two established formulas — Epley and Brzycki — at once, so you see the range rather than relying on one estimate.
- It lets you gauge your max from a submaximal set, avoiding the injury risk of a true one-rep attempt.
- The estimate works for any lift and any weight unit, since it depends only on reps and load.
- It runs instantly in your browser with no sign-up.
Frequently Asked Questions
How is one-rep max estimated from multiple reps?
Formulas like Epley (weight × (1 + reps/30)) and Brzycki (weight ÷ (1.0278 − 0.0278 × reps)) use the relationship between the load you lifted and how many reps you managed to project the weight you could lift just once. Fewer reps give a more accurate estimate.
Why do Epley and Brzycki give different numbers?
They are different mathematical models fitted to strength data, so they diverge slightly, especially at higher rep counts. Showing both gives you a realistic range rather than a single false-precision figure — your true max likely sits near them.
How many reps should I use for the best estimate?
Estimates are most accurate from sets of around 2 to 6 reps. Beyond about 10 reps, fatigue and technique introduce more error, so the projection becomes less reliable. Use a challenging but clean set in the lower rep range.
Should I actually test my true one-rep max?
Estimating is safer and sufficient for most training purposes. A true max attempt carries injury risk and requires proper warm-up, technique, and ideally a spotter, so many lifters rely on calculated estimates for programming instead.
