One-Rep Max
WEBEstimate your one-rep max from weight and reps, with a training percentage table.
Estimates are for training guidance, not a guaranteed max. Warm up, use a spotter, and never grind a true single you are not ready for.
What is the One-Rep Max tool?
This one-rep max calculator estimates your 1RM — the heaviest weight you could lift for a single rep — from a set you have already done, so you never have to test a true maximal single to program your training. Enter the weight you lifted and how many clean reps you managed, pick kilograms or pounds, and it returns your estimated one-rep max instantly.
It uses the two most trusted strength formulas side by side: Epley (1RM = weight × (1 + reps ÷ 30)) and Brzycki (1RM = weight × 36 ÷ (37 − reps)). Both are shown at once so you can compare — they agree closely in the low-rep range where estimates are most reliable, and drift apart as reps climb. Under the result you also get a full percentage-of-1RM table so you can read off your working loads for 95%, 90%, 85% and on down, and a rep-target table showing the weight to aim for at 2 through 10 reps.
Everything runs entirely in your browser — nothing you type is uploaded, stored or sent to any server, and no account is needed. It is free, works on your phone at the gym, and switches between kg and lb in one tap. One honest note: an estimated 1RM is a programming tool, not a guaranteed number on the bar. Estimates are most accurate under about five reps; the more reps you use, the rougher the guess. Always warm up, use a spotter, and only attempt a real max when you are ready for it.
How to use the One-Rep Max
- Choose your unit — kilograms or pounds.
- Enter the weight you lifted for your set.
- Set the number of reps you completed with the stepper.
- Read your estimated one-rep max, with the Epley and Brzycki values side by side.
- Use the % of 1RM table to pick your working loads, or the rep-target table to plan sets of 2–10 reps.
- Switch the formula toggle to compare Epley and Brzycki any time.
Frequently asked questions
What is a one-rep max (1RM)?
Your one-rep max is the most weight you can lift for a single, full repetition of an exercise. It is the benchmark strength coaches use to set training intensities — for example, a hypertrophy block might sit at 70–80% of 1RM and a strength block at 85%+.
Which is more accurate, Epley or Brzycki?
Neither is universally 'right' — both are well-validated estimates. They give almost identical numbers at low reps (1–5), which is where any 1RM prediction is most trustworthy. As reps rise, Epley tends to predict a slightly higher max and Brzycki a slightly lower one, so seeing both gives you a sensible range rather than a single false-precision figure.
How many reps should I use for the best estimate?
Use a set taken close to failure with about 2–6 reps. The formulas are most reliable in that range. Above roughly ten reps the estimate becomes rough, because factors like muscular endurance and fatigue start to matter more than raw strength.
How do I turn my 1RM into training weights?
Read them straight off the % of 1RM table below the result. Multiply your one-rep max by the percentage a programme calls for — the calculator has already done this for 100% down to 60% in 5% steps — so you can load the bar without doing the maths at the gym.
Is my data private?
Yes. The weight and reps you enter are processed entirely in your browser — nothing is uploaded, stored or sent to a server. Once the page has loaded, the calculator even works offline.
Is this one-rep max calculator free?
Yes — free, with no sign-up, no account and no limits. Open it, enter a set, and read your estimated 1RM in seconds.