One-Rep Max (1RM) Calculator

What does my one-rep max result mean?

Your estimated max is a rough weight you might lift once, worked out from the set you entered. Epley and Brzycki take different routes to that number, and the gap only shows their disagreement. Even if they agree, your technique and how you feel that day can change what you lift.

Take 100 kg for five reps: Epley gives about 116.7 kg and Brzycki about 112.5 kg, leaving a gap of 4.2 kg. Their 75 percent rows then give 87.5 kg and 84.4 kg, so the choice of formula carries into the chart.

The Epley vs Brzycki explainer walks through that set in more detail and explains the estimate Kinoku charts.

The formulas behind the charts

The Epley formula comes from Boyd Epley's 1985 Poundage chart, which we haven't found in a stable web copy. Matt Brzycki published the other formula in 1993, and his paper has an author-uploaded copy alongside the publisher record.

Epley:   max = weight × (1 + reps / 30)
Brzycki: max = weight × 36 / (37 − reps)
Percent: load = estimated max × percent / 100
Epley rep load (2–10): max / (1 + reps / 30)
Brzycki rep load (2–10): max × (37 − reps) / 36

We keep both formulas as written, including what happens with a single. At 100 kg for one rep, Epley gives 103.3 kg and Brzycki gives 100 kg. The Epley calculation matches the one in Kinoku's Stats chart.

The calculator works in kilograms, then uses 2.20462 pounds per kilogram when you switch units. It accepts whole rep counts from one to thirty-six; Brzycki divides by zero at thirty-seven, though high-rep sets weaken the estimate long before that.

The caution about high reps comes from Mayhew and colleagues' 2008 study, of young women doing bench press, which found more accurate predictions below ten reps. It gives a reason to be cautious with high-rep sets, but no personal error range for your lift.

Privacy

The maths happens in your browser, and changing the set or units makes no network requests. Your entries aren't stored or sent anywhere, so opening the page again brings back the example set.

Common questions

Can I use this as a bench press max calculator?

You can enter a bench press set, a squat or another lift measured in weight. The formula only sees the weight and completed reps, so it can't account for your technique or the reps you had left.

Why does one rep give two different estimates?

Epley adds one thirtieth of the weight even for a single, giving 103.3 kg from a 100 kg lift. Brzycki gives 100 kg for the same set; we keep the formulas as written, including that difference.

Does the chart round to the plates in my gym?

Each row uses the full estimate, then rounds the displayed weight to one decimal place. That might land between loads your plates can make, because the chart doesn't know which plates you have or choose a training plan.

Why can I enter 36 reps but not 37?

Brzycki divides by 37 minus your rep count, so entering 37 would mean dividing by zero. The useful range ends much earlier than that maths limit, which is why sets above ten reps get a caution beside the result.

How do I print just the percentage and rep-max charts?

The print button opens your browser's print dialog with the set, both estimates and both tables on one page. The layout fits A4 or US Letter at normal scale, with the site navigation and longer explanations left out.