Estimating your one-rep max
Your one-rep max, or 1RM, is the heaviest weight you can lift once with good form. It is the standard way to compare strength, and many programs set your weights from it.
You don't need to test it. Maxing out is tiring, takes a full session, and carries more risk than normal training. An estimate from a normal heavy set is close enough for almost every purpose.
The estimate
Several formulas turn a weight and a rep count into an estimated max. One of the most used is the Epley formula: weight × (1 + reps ÷ 30).
For 100 kg × 5 reps: 100 × (1 + 5 ÷ 30) = 100 × 1.167, which is about 117 kg. For 80 kg × 10: 80 × 1.333, about 107 kg.
Other formulas, such as Brzycki, give slightly different answers, usually within a few kilos of each other at low reps.
How far to trust it
Estimates are most accurate from sets of about 2 to 6 reps. The further you get from one rep, the less the formula knows about you. Some people are better at high reps and some at low reps, so a set of 15 can over- or under-estimate your max by quite a lot.
The set has to be a real effort. A set of 5 that you could have done for 8 will give you an estimate that is too low. A set where your form broke down will give one that is too high.
Treat the number as a guide, good for tracking your progress and setting training weights, not as a promise of what you would lift on the day.
Use the same formula over time and the trend is meaningful even if the exact number is a few kilos off.
What it is useful for
Tracking strength. Your estimated max goes up when you lift more weight for the same reps or more reps for the same weight, so it shows progress in one number, whatever rep range you trained in.
Setting a training max. Percentage programs work off a number a little below your max. Estimate the max, take 85 to 90% of it, and you have your training max without ever testing.
Picking working weights. Charts of percentages tell you roughly how heavy to go for a given number of reps, for example about 85% of your max for a set of 5 to 6.
If you do want to test
Test only on a lift you know well, after a proper warmup, with a spotter or safety bars. Work up in small jumps with long rests, and stop at a weight you lift with good form rather than grinding a rep you are not sure of. Most programs don't ask for it, and many lifters go years without a true max test.
Estimated 1RM in Durata
Durata uses the Epley formula everywhere: the estimated 1RM charts on each exercise, your e1RM records, the Strength Index and goals. A single rep counts as exactly the weight lifted.
Warmup sets, partial reps and Rest Pause groups are left out of your best estimated max, because they would make it read higher than it should.
In a workout, the 1RM button opens the rep max calculator: give it a weight and reps and it shows your estimated max and a table of what you could lift for other rep counts.
Common questions
How do I calculate my one-rep max without testing it?
Take a hard set of 2 to 6 reps and use a formula. With the Epley formula, weight × (1 + reps ÷ 30), 100 kg for 5 reps gives about 117 kg.
How accurate are one-rep max calculators?
Close enough to train with, especially from sets of 2 to 6 reps done to a real effort. The further from one rep, the bigger the error.
Which formula does Durata use?
The Epley formula, everywhere in the app, so your charts, records and goals all agree.
Should I test my one-rep max?
You rarely need to. An estimate from a heavy set is enough to track progress and set training weights, with less tiredness and risk.
Put it into practice
Durata is free to use — 50 proven programs, automatic progression, rest timers and PR tracking, all on your phone.