Health and Fitness Calculators
One-Rep Max
Your one-rep max is the heaviest weight you could lift once for a given exercise. Estimating it from a set you have already done is safer than testing it, and it is the figure most strength programs set their percentages against.
Epley estimate: 0.
Brzycki estimate: 0.
How it works
Both formulas work from the same observation, that the weight you can lift falls off in a predictable way as the repetitions go up. They disagree slightly, and seeing both is more honest than picking one and calling it the answer.
Epley: 1RM = weight × (1 + repetitions ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 - repetitions)
Five repetitions at 100 kg gives 100 × (1 + 5 ÷ 30) by Epley, which is about 117 kg, and 100 × 36 ÷ 32 by Brzycki, which is about 113 kg.
Why you have to type this one in
Every other calculator here can read your own figures. This one cannot, and the reason is worth stating plainly. Strength apps record an exercise as its heaviest weight together with all the repetitions you did across every set, so five sets of five at 100 kg reaches us as one hundred kilograms and twenty-five repetitions. Put those two numbers into the formula and it reports a one-rep max near 183 kg against a true figure around 113 kg. A confidently wrong answer about how much you can lift is one somebody might try, so this page asks you for the set instead.
What this number is not
It is not a weight you should go and attempt. It is an estimate for setting training percentages, and a genuine maximum attempt needs a warm-up, a spotter and a reason.
How accurate it is
Both formulas are reliable up to about five repetitions and drift upward after that, because at high repetitions you are measuring endurance rather than strength. Above ten repetitions treat the estimate as a rough indication only.
Common questions
Which formula should I use?
Brzycki is usually a little conservative and Epley a little generous, and the gap widens as the repetitions go up. If you are setting training weights from it, the lower of the two is the safer choice.
How many repetitions should the set be?
Three to five, taken close to failure. Fewer than three and a single bad rep swings the answer; more than eight and you are measuring something other than maximum strength.
Will FitnessSyncer ever work this out from my logged sets?
Not from what we receive today, because the repetitions arrive summed across the sets rather than attached to the heaviest one. If that changes, this page will read your own lifts.
