One-Rep Max Calculator
Estimate your 1RM from a lighter set using the Epley and Brzycki formulas, with training percentages.
Find your max without maxing out
Testing a true one-rep max is risky and tiring, so lifters estimate it from a heavier set they can already complete safely. This tool applies the two most trusted formulas — Epley and Brzycki — to your weight and reps, giving a reliable strength benchmark to program around.
For example, 100 kg for 5 clean reps estimates roughly a 117 kg max by Epley. The two formulas agree closely at low reps and diverge as reps climb, which is why testing with ten reps or fewer keeps the estimate honest.
Turn it into training loads
The result also breaks your estimated max into percentage loads, so you can pull the right weight for strength, hypertrophy, or speed work. It all runs in your browser and nothing you enter is uploaded.
Frequently Asked Questions
How is one-rep max estimated?
From a set you can complete with good form. The tool shows both the Epley formula (weight × (1 + reps/30)) and the Brzycki formula (weight × 36 / (37 − reps)), which agree closely at low reps.
How many reps should I test with?
Estimates are most accurate at 10 reps or fewer. Above about 12 reps the formulas drift, so use a heavier weight for a lower rep count when you can.
What are the percentage loads for?
They turn your estimated max into working weights — for example 80% for strength or 65% for volume — so you can program sessions without maxing out.
Is my data uploaded?
No. Everything is calculated in your browser and nothing you enter is stored or sent anywhere.
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