What’s your one-rep max? This free 1 rep max calculator estimates your 1RM from a weight and reps using the Epley and Brzycki formulas, plus a percentage table for picking training weights — no max attempt needed.
Your lift
reps
Enter a weight and the reps you completed with good form (ideally under 10 for accuracy). Your one-rep max is estimated — don’t attempt a true max without proper warm-up and a spotter.
Estimated 1 rep max
— kg
Enter weight and reps
Epley
—
Brzycki
—
An estimate from a rep test — accuracy is best at lower reps and drops as reps rise. Use percentages as a starting point for programming, and always train with good form and safety.
Use this free 1 rep max calculator to estimate the most you could lift for a single rep. Enter a weight and the reps you completed to get your estimated one-rep max (1RM) and a training percentage table.
What this 1 rep max calculator shows you
A one-rep max calculator estimates your 1RM — the maximum weight you could lift once — from a set you’ve already done. It uses two trusted formulas (Epley and Brzycki), averages them, and builds a table of training percentages so you can pick working weights without testing a true max.
Lift 100 kg for 5 reps and your estimated 1RM is about 115 kg. Accuracy is best at low reps (ideally under 10) — the more reps you do, the rougher the estimate becomes.
Training percentages of 1RM
% of 1RM
Approx. reps
Typical use
100%
1
Max strength test
90%
~4
Strength
80%
~8
Strength / hypertrophy
70%
~12
Hypertrophy / volume
How to use the 1RM calculator
Enter the weight you lifted (tap to switch kg/lb).
Enter the reps you completed with good form.
Read your estimated 1RM and the percentage table for programming.
A note on safety
This is an estimate, not a reason to attempt a true max. If you ever test a genuine 1RM, warm up thoroughly, use a spotter or safety bars, and never sacrifice form for weight. Estimating from a rep set is safer and good enough for most training.
1 Rep Max FAQ
How do I calculate my 1 rep max?
Enter a weight and the reps you completed; the calculator applies the Epley and Brzycki formulas and averages them. For example, 100 kg for 5 reps estimates a 1RM of about 115 kg.
How accurate is a 1RM estimate?
It's most accurate at low reps — ideally under 10. The more reps you perform, the less precise the estimate, because rep performance varies more at high volumes.
What are the Epley and Brzycki formulas?
They're two widely used 1RM equations. Epley is weight × (1 + reps/30); Brzycki is weight × 36 ÷ (37 − reps). This calculator shows both and averages them.
How do I use training percentages?
Once you know your estimated 1RM, percentages set working weights: roughly 90% for ~4 reps, 80% for ~8, 70% for ~12. The table does the maths for you.
Should I test a true 1 rep max?
It's not necessary for most people and carries injury risk. Estimating from a rep set is safer. If you do test, warm up thoroughly, use a spotter or safety bars, and keep strict form.
Is the 1 rep max calculator free to use?
Yes, this 1 rep max calculator is completely free, needs no sign-up, and gives instant results in your browser.
