One rep max calculator: estimate your 1RM
Enter a weight and the number of reps you completed: the calculator estimates your one rep max without you having to test it.
From 1 to 10, with good form.
Estimated 1RM
91.7 kg
Epley: 93.3 kg · Brzycki: 90 kg
Estimated weights by number of reps
| Reps | Weight | % of 1RM |
|---|---|---|
| 1 | 91.5 kg | 100 % |
| 2 | 87.5 kg | 95 % |
| 3 | 85 kg | 93 % |
| 4 | 82.5 kg | 90 % |
| 5 | 80 kg | 87 % |
| 6 | 77.5 kg | 85 % |
| 7 | 75.5 kg | 82 % |
| 8 | 73 kg | 80 % |
| 9 | 71 kg | 77 % |
| 10 | 69 kg | 75 % |
Weights rounded to the nearest 0.5 kg.
What is a 1RM?
Your 1RM, or one repetition maximum, is the heaviest weight you can lift once with good form. It is the reference used to set the intensity of a strength program. Testing it for real takes a long warm-up, often a spotter, and leaves a lot of fatigue: estimating it from a lighter set is simpler and safer.
How the calculation works
The calculator uses the two most common equations:
- Epley (1985): 1RM = weight × (1 + reps ÷ 30)
- Brzycki (1993): 1RM = weight × 36 ÷ (37 − reps)
Both give exactly the same result at 10 reps and drift slightly apart below that. The displayed result is their average, and each value stays visible so you can compare them. The table inverts the same equations to estimate the weight to use for a given number of reps.
Why no more than 10 reps
In 2006, Jeffrey Reynolds and colleagues tested 70 people on 1, 5, 10 and 20 rep maxes on the bench press and the leg press. Weight does not drop linearly as reps go up, and the 5-rep set predicted 1RM most accurately. The authors conclude that no more than 10 reps should be used with this type of equation, so the calculator does not accept longer sets.
For a reliable estimate, use a set taken close to failure, ideally around 5 reps, on an exercise you are comfortable with.
The limits of an estimate
An equation gives an average. In the same study, the relationship between reps and weight was not the same on the bench press and the leg press: depending on the exercise and the person, your true 1RM can be a few kilos off. Use it as a starting point, not as a record to beat.
Sources
- Epley B., "Poundage Chart", Boyd Epley Workout, Body Enterprises, Lincoln (Nebraska), 1985.
- Brzycki M., "Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue", Journal of Physical Education, Recreation & Dance, 1993.
- Reynolds J.M. et al., "Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry", Journal of Strength and Conditioning Research, 2006.
Let Loaden pick the weight
Loaden suggests the weight for each session based on your previous performance, so you never have to do the math.
