Estimated 1RM Calculator
The Estimated 1RM Calculator estimates the heaviest weight you could lift for a single repetition, from the number of repetitions you can perform with a given weight on a movement.
Knowing your one-repetition maximum (1RM) on a movement is necessary for following programmes built on training percentages; but a genuine maximum attempt is both tiring and demanding on technique. This tool offers a reasonable estimate without that attempt: the weight and the number of repetitions of a set you complete comfortably carry a surprising amount of information about your maximum.
Tool
Frequently asked questions
Why was the Epley formula chosen?
Epley is one of the most widely used and most easily remembered formulas in the field; in the low repetition range it gives results that largely agree with the other well-known formulas.
How many repetitions should the set I enter have?
A set of between 2 and 6 repetitions, taken close to the repetition limit, produces the most accurate estimate. A single-repetition set is already very close to the maximum, while anything above 10 repetitions weakens the estimate.
Do I need a separate 1RM estimate for each movement?
Yes; 1RM is specific to the movement. Your squat estimate says nothing about your deadlift, because each movement uses different muscle groups and technical skills.
My estimate is lower than last month; am I going backwards?
A single measurement is no proof of decline; sleep, nutrition and the fatigue of the day all affect a set. Looking at the trend over a few weeks is always more informative than looking at a single day.
Method and formula
The calculation is based on the Epley formula, one of the most widely used equations for this purpose: estimated 1RM = weight × (1 + reps / 30). If you can perform 5 repetitions with 80 kg, for instance, the estimate comes to 80 × (1 + 5/30) ≈ 93 kg. The formula is at its most reliable at low repetition counts; on sets above 10 repetitions the endurance component grows and the estimate loses reliability markedly, and the tool warns you when that happens.
How to read the result
Use the figure produced not as “the weight I could try tomorrow” but as a reference for working out programme percentages: a set to be performed at 70%, for example, is 0.7 times the estimated 1RM. The estimate is more accurate on some movements than on others; it is generally more consistent in experienced lifters and on the large compound lifts. It is also normal for different formulas to give results a few kilograms apart from the same inputs.
Limits
- The estimate assumes the set entered was genuinely taken close to the repetition limit; a cautious set will not produce a high estimate.
- On sets above 10 repetitions the reliability of the formula falls markedly.
- Factors such as daily form, sleep and technique shift the true maximum from day to day.
- The formula cannot know whether your technique will hold at that load; the estimate is a mechanical number.
Safety boundary
Do not read the estimated figure as an invitation to attempt a genuine maximum. Heavy single attempts call for experience, a proper warm-up and a spotter; beginners are not advised to test their 1RM. In the case of any pain or injury, consult a specialist before attempting heavy loads.
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