Estimate your 1RM from any set with Epley and Brzycki, plus a percentage table to plan the session.
Your one-rep max is the heaviest weight you can lift once with good technique, and it is the reference almost every strength programme is written around. Actually testing it is slow and risky, so coaches estimate it from a set you already do safely. This calculator applies the two formulas that dominate the field: Epley, which adds one thirtieth of the weight for every repetition, and Brzycki, which divides by a term that shrinks as the set gets longer. Lifting 100 kg for 5 repetitions gives 116.7 kg by Epley and 112.5 kg by Brzycki, so the calculator shows both and reports their average, 114.6 kg.
Seeing the two side by side is the point. Up to about six repetitions they agree within a kilo or two; beyond that they diverge, with Epley the more generous of the pair, and the gap between them is a useful measure of how much you should trust the estimate at all. Above roughly ten repetitions both start to overshoot, because a long set is limited as much by fatigue, breathing and grip as by pure strength — two people with the same 1RM can be several repetitions apart at 70%. The percentage table below the result turns the estimate into training loads using the classic anchors: 95% for doubles, 90% for fours, 85% for sixes, 80% for eights, 75% for tens and 70% for twelves.
Use the numbers as a starting point and let the bar have the final word. Estimates shift with the exercise (they hold up better on squat and bench press than on isolation movements), with training age, with how rested you are and with how strictly you count a repetition. A real 1RM attempt is a maximal effort that needs a full warm-up, solid technique and a spotter, which is exactly the risk this calculation is meant to avoid. This is informational content, not coaching or medical advice, and the whole thing runs in JavaScript on your own device — nothing you type leaves the page.
Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki: 1RM = weight × 36 ÷ (37 − reps). The headline figure is the average of the two; with a single repetition both collapse to the weight itself. Training loads come from multiplying the estimated 1RM by 95%, 90%, 85%, 80%, 75% and 70%, which correspond roughly to 2, 4, 6, 8, 10 and 12 repetitions.
Take a set you completed with good form and apply Epley — weight × (1 + reps ÷ 30) — or Brzycki — weight × 36 ÷ (37 − reps). For 100 kg × 5 that is 116.7 kg and 112.5 kg, an average of 114.6 kg.
Neither wins outright: they agree closely up to about six repetitions, and past that Epley returns the higher number. Averaging them, as this calculator does, is the usual compromise when you have no reason to prefer one.
Between three and six gives the most reliable result. Above ten the estimate drifts, because endurance and technique start limiting the set more than maximal strength does.
Multiply it by the percentage for the effort you want: 85% for sets of six, 80% for eights, 70% for twelves. The table under the result does that for you, and you should still adjust to how the weight feels that day.
Only with solid technique, a proper warm-up and someone spotting you — and it is not necessary for most people. Estimating from a submaximal set gives you a usable number without the maximal attempt.
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