1RM Calculator
Enter the weight you lifted and how many reps you hit, and get an estimated one-rep max — plus what to load for every other rep count.
Estimated one-rep max
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kg
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| Reps | Weight | % of 1RM |
|---|---|---|
| 1 | — | — |
| 2 | — | — |
| 3 | — | — |
| 4 | — | — |
| 5 | — | — |
| 6 | — | — |
| 8 | — | — |
| 10 | — | — |
| 12 | — | — |
These are estimates. Actual performance varies with fatigue, technique and the lift itself — use a spotter or safety pins if you test a true single.
How this is worked out
Every formula here estimates a maximal single from a submaximal set. None of them measures anything — they fit a curve through what lifters typically manage, and your own curve is yours.
Epley is the default because Beacon uses it. Your strength projection in the app is weight × (1 + reps ÷ 30), the same arithmetic this page runs, so the number here and the number in the app agree for the same set. A calculator that quietly used a different formula would hand you two answers and no way to tell which one the app meant.
The others are here because the published research disagrees about which fits best, and the disagreement is worth seeing. At two to five reps they land within about eight percent of each other; at twelve they spread by more than twelve. That is the argument for keeping your test sets short — not for picking a favourite formula.
Most of that low-rep gap is one formula. Mayhew was fitted on the bench press and reads highest of the seven at every rep count under six, so it is the one most likely to disagree with the rest on a squat or a deadlift.
Using the load table
The loads are derived from your estimated max with the same formula, run backwards — so they are consistent with the estimate above them, not borrowed from a generic percentage chart. They are a starting point for programming, not a prescription: how many reps you actually have at a given percentage depends on the lift, the day and how you have been sleeping.
One quirk worth knowing
Enter a true single and Epley will estimate about three percent above the weight you just lifted. That is not a bug in this page: Epley is fitted to multi-rep sets and is not the identity at one rep. Brzycki and Lombardi do return the weight itself. If you have actually tested a single, that number is your max — no formula improves on it.
Frequently asked
What is a one-rep max?
The heaviest weight you could lift for a single clean repetition. It is the usual reference point for setting training loads, because most programmes are written as a percentage of it.
Which formula should I use?
Epley is the default here because it is the one Beacon uses for your strength projection, so the app and this page will not disagree about the same set. Brzycki is often closest at ten reps or fewer; Wathan holds up better at higher reps. At two to five reps they land within about eight percent of each other; at twelve they spread by more than twelve — so keep test sets short rather than hunting for the right formula.
How many reps give the best estimate?
A hard set of two to five, with form you would not be embarrassed by. Every formula here extrapolates from submaximal work, and the further it has to reach the less it knows. Past about twelve reps you are measuring conditioning as much as strength, and the estimate drifts high.
Is an estimated 1RM the same as a tested one?
No. It is a prediction from a set you did, not a measurement. Your real max moves with sleep, stress, technique and how the day is going, which is exactly why most people train off an estimate instead of testing often.
Should I test my actual max?
Rarely, and never alone. A true single is a maximal effort with maximal consequences for a technique breakdown — use a spotter or safety pins, and do not test on a day you already feel beaten up.
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