Free tool
1RM Calculator
Estimate your one-rep max from any hard set. Enter the weight you lifted and how many reps you managed, and the calculator returns your estimated 1RM plus a full table of training loads at every percentage of it — in kilograms or pounds.
How the estimate works
A one-rep max calculator predicts the most you could lift for a single rep from a set you’ve already done. It works because the weight you can move and the reps you can get with it are closely related: the more reps a load allows, the further it sits below your true max. This tool uses the mean of two well-established formulas — Epley and Brzycki — to turn your set into a single estimate.
How accurate is it?
Treat the result as a well-reasoned estimate, not a tested number. Rep-based predictions are most reliable when the set is genuinely hard — taken to within a rep or two of failure — and kept low. Accuracy is strongest at 2–6 reps and loosens as reps climb, so this calculator accepts 1–10 reps and flags how much confidence to place in each result. Your best guide is always a max you’ve actually tested under good conditions.
Using the % of 1RM table
Most programmes prescribe work as a percentage of your 1RM — a heavy top set at 90%, back-off work at 70%, volume at 60%. The table below your result does that maths for you, rounded to practical plate increments, so you can load the bar without a spreadsheet. The rep figures beside each percentage are rough guides, not targets.
Questions, answered
What is a one-rep max (1RM)?
Your one-rep max is the heaviest weight you can lift for a single rep of an exercise. It’s the standard reference point for setting training loads — most programmes prescribe work as a percentage of it.
How accurate is a 1RM calculator?
It’s an estimate, not a measurement. Rep-based formulas are most reliable when the set is taken close to failure and kept to a low number of reps. Accuracy is best at 2–6 reps and drifts as reps rise, which is why this tool caps input at 10.
How many reps should I enter?
Use a set you took close to failure (roughly 0–1 reps left in the tank). A hard set of 2–6 reps gives the most trustworthy estimate. If you enter a single rep, the tool simply returns that load — it’s already a true max, not an estimate.
Which formula does this use?
The estimate is the mean of the Epley and Brzycki formulas. Averaging the two cancels the slight upward bias Epley carries at low reps, giving a steadier single number without pretending to a precision the maths doesn’t have.
Should I actually attempt a true 1RM?
You don’t need to. Estimating from a hard set of a few reps avoids the fatigue and injury risk of a genuine maximal single, while still giving you a number to programme around.
Track your 1RM the easy way
When KOVA launches, it’ll estimate your 1RM automatically as your working sets improve, track your PRs, and show your strength trends over time — so you never have to reach for a calculator. Join the waitlist to be first to know when it goes live.
More from KOVA: what KOVA does · the blog