Your one-rep max (1RM) is the most weight you can lift for a single repetition of an exercise. Instead of risking a true max attempt, enter a weight you lifted and how many clean reps you managed — the tool estimates your 1RM with two well-known formulas and shows what to load for each training percentage. It calculates on your device, in kilograms or pounds.
Enter a weight and reps to estimate your one-rep max.
This is an educational estimate, not a guaranteed lift. Warm up, use good form, and consider a spotter for heavy attempts. Consult a coach or doctor if unsure.
How it works
Two formulas do the work. Epley estimates 1RM as weight × (1 + reps ÷ 30); Brzycki as weight × 36 ÷ (37 − reps). They agree closely at low rep counts and drift apart as reps rise, so the tool reports both and their average as your headline estimate. A single-rep set is treated as its own 1RM rather than being inflated.
From the estimate it builds a percentage table — 95% down to 60% — with the load for each and the reps you can typically hit there. These formulas are calibrated for roughly 1–10 reps; beyond about 12 the relationship between reps and max becomes unreliable, so the tool caps reps at 12. Treat the number as a training guide, not a guaranteed lift.
Practical examples
Bench press for 5 reps
You benched 100 kg for 5 clean reps. Epley says 116.7 kg, Brzycki 112.5 kg, so your estimated 1RM is about 114.6 kg. Your 80% working weight would be around 92 kg.
A true single
If you actually hit 1 rep at 140 kg, that 140 kg is your 1RM — the tool doesn’t add anything on top. The percentage table then plans your next lighter sessions off it.
Planning a training block
With a 150 kg squat 1RM, the table gives 127.5 kg for 6 reps (85%) and 112.5 kg for 10 reps (75%) — ready-made loads for a strength or hypertrophy week.
Frequently asked questions
How accurate is an estimated 1RM?
For sets in the 1–5 rep range it’s usually within a few percent of a true max. Accuracy falls as reps climb because more reps depend on endurance, not just strength. Use fewer, clean reps to failure for the best estimate.
Why do Epley and Brzycki give different numbers?
They were fitted to different data with slightly different curves. Epley tends to read a touch higher at moderate reps, Brzycki a touch lower. Averaging them smooths out the disagreement, which is why the tool shows the mean as the main figure.
Should I actually test my true 1RM?
Rarely, and only when trained and warmed up, ideally with a spotter. Maximal singles carry injury risk and heavy fatigue. Estimating from a submaximal set gives you most of the information with none of the danger.
What counts as a "clean" rep?
A rep through the full range of motion with good form and no help from a spotter. Grinding, partial, or assisted reps inflate the count and push the estimate too high. Stop at the last rep you could do properly.
Why is the rep count capped at 12?
Beyond about 12 reps the formulas lose their footing — a 20-rep set says more about your conditioning than your maximal strength. Keeping to 12 or fewer keeps the estimate meaningful.
What are the percentages for?
They translate your max into everyday training loads. Strength work often lives at 80–95%, hypertrophy around 65–80%. The table gives you the weight and typical reps for each so you don’t have to do the maths mid-session.
Does it work for any lift?
The formulas are general, so they apply to squats, bench, deadlift, press and similar barbell lifts. They’re least reliable for very technical or explosive movements, where fatigue and skill affect reps more than raw strength.
Kilograms or pounds?
Either. The maths is unit-free — switch the toggle and the same numbers are simply labelled kg or lb. Just keep your input and reading in the same unit.
Is anything I enter stored?
No. The calculation runs entirely in your browser. Your lifts aren’t uploaded and analytics never receives them.
Related tools
Calorie Calculator
Estimate your daily calories to maintain, lose or gain weight, from BMR and activity level (Mifflin–St Jeor). An educational estimate.
Health & fitness
Macronutrient Calculator
Turn a daily calorie target into grams of protein, carbs and fat for a balanced, low-carb, high-protein or keto split. An educational estimate.
Health & fitness
Pace Calculator
Work out running pace, finish time or distance from any two of them — in minutes per km or per mile.
Health & fitness
BMI Calculator
Calculate your Body Mass Index from height and weight, with the WHO category and your healthy-weight range. An educational estimate.
Health & fitness
Ideal Weight Calculator
Estimate a healthy weight for your height and sex, via the Devine, Robinson, Miller and Hamwi formulas plus the BMI range. An educational estimate.
Health & fitness
Body Fat Calculator
Estimate body fat percentage from tape measurements using the U.S. Navy method, with fat and lean mass. An educational estimate.
Health & fitness