One Rep Max Calculator
This free one rep max calculator estimates your 1RM from a weight and rep count, using the Epley and Brzycki formulas, plus a training percentage table for programming sets. Nothing you enter is sent anywhere or stored.
How to Use It
- Enter the weight you lifted and the number of reps you completed in that set (1 to 12).
- Your estimated one rep max, from both the Epley and Brzycki formulas, updates instantly.
- Use the training percentage table below to plan sets at a target intensity.
How It Works
The Epley formula estimates one rep max as weight times one plus reps divided by thirty. The Brzycki formula estimates it as weight times thirty six, divided by thirty seven minus reps. The two formulas behave a little differently at the edges: at exactly one rep, Brzycki reduces to exactly the weight you entered, while Epley gives a figure a few percent higher, a real difference between the formulas rather than a bug in either one. The headline estimated one rep max shown here is the average of both, a common way to get a single, more robust number.
Formulas
Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Estimated 1RM = (Epley + Brzycki) ÷ 2
A worked example: a weight of 185 for 5 reps gives an Epley estimate of 215.8, a Brzycki estimate of 208.1, and an averaged estimated one rep max of 212. The training percentage table then takes that 212 figure and shows the working weight at 100%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, and 60% of it, the standard percentages used for programming strength training.
This is a training planning estimate based on common strength coaching formulas, not a measured maximum or a medical assessment. Everything runs client-side in your browser. Nothing you enter is sent anywhere or stored.
Frequently Asked Questions
Why does this show two different formulas instead of one number?
The Epley and Brzycki formulas are both well established, and they can disagree meaningfully, especially at higher rep counts, without either one being universally regarded as more accurate. Showing both, along with their average as the headline estimate, gives a more honest picture than presenting a single formula as a definitive answer.
Why is the rep count capped at 12?
Every rep max formula loses accuracy sharply beyond roughly 10 to 12 reps, where a set becomes increasingly limited by muscular endurance rather than pure strength. Capping the input at 12 avoids quietly extrapolating a number that formulas like these were never designed to estimate.
What is the training percentage table for?
Strength programs are commonly written as a percentage of your one rep max, for example five sets at 80% for a strength phase, or lighter sets at 60 to 65% for technique work. The table converts your estimated one rep max into the actual weight for each common training percentage, so you can plan sets without recalculating a max every session.
Does this measure my overall fitness?
No, it estimates strength for the specific lift and weight you entered, not general fitness or conditioning. A one rep max for the bench press, for example, says nothing about your squat or your cardiovascular fitness; each lift needs its own estimate.
Is this a substitute for actually testing my one rep max?
No, it is a training planning estimate from a formula, not a measured maximum. If you want to attempt a true one rep max, do it with proper form, a full warm-up, and ideally a spotter or coach, not as a first-time solo attempt based on a number from this calculator.