One-Rep Max Calculator: Estimate Your 1RM
Estimate how much weight you can lift for one repetition based on the weight and repetitions of a completed set.
Use a challenging set completed with consistent technique.
Estimated one-rep max (Brzycki)
112.5
kg
Based on 100 kg for 5 repetitions.
Training weights by percentage
100%
112.5 kg
95%
106.9 kg
90%
101.3 kg
85%
95.6 kg
80%
90 kg
75%
84.4 kg
70%
78.8 kg
65%
73.1 kg
60%
67.5 kg
55%
61.9 kg
50%
56.3 kg
How to use the one-rep max calculator
- Choose kilograms or pounds.
- Enter the weight lifted and the number of completed repetitions.
- Choose Brzycki, Epley, or Lombardi. Brzycki is the default.
- Calculate to see the estimated one-rep max and percentage-based training weights.
Use a challenging set of 1 to 12 repetitions completed with consistent technique. The result is an estimate, not a tested maximum.
Methodology and formulas
The calculator applies the selected repetition-based equation and rounds the result to 0.1 kg or lb.
- Brzycki:
1RM = weight / (1.0278 - 0.0278 x repetitions) - Epley:
1RM = weight x (1 + repetitions / 30) - Lombardi:
1RM = weight x repetitions^0.10
Different formulas can return different estimates from the same set. Switching formulas lets you see that variation without changing the input.
Worked example
With 100 kg for 5 repetitions, the Brzycki formula estimates 112.5 kg:
100 / (1.0278 - 0.0278 x 5) = 112.5 kg
The percentage table then shows 90 kg at 80 percent of the estimate.
Using the estimate
- Use it as a repeatable reference for planning loads and tracking changes.
- Compare results for the same exercise, formula, technique, and repetition range.
- Treat the displayed percentage weights as arithmetic references, not prescribed training loads. Training intensity: RPE, RIR, and percentage of 1RM explains what a percentage of 1RM does and does not tell you about a set.
- The GymEvo app keeps the same estimate in your exercise history and can also manage weight and rep progression for each exercise you train.
- To compare sessions with it over time, see how to track progressive overload, or the complete guide to progressive overload for what to change once you can read the trend.
Assumptions and limitations
- Repetition-based formulas estimate rather than directly test a one-rep max.
- The estimate can vary with exercise, technique, range of motion, fatigue, and how close the set was to failure.
- Accuracy can decrease as the repetition count rises, so the calculator accepts no more than 12 repetitions.
- Do not attempt a maximal lift only because a calculator produced a number.
Sources
- Strength Testing: Predicting a One-Rep Max from Reps-to-Fatigue — Journal of Physical Education, Recreation & Dance (accessed 2026-09-02)
- The Accuracy of Prediction Equations for Estimating 1-RM Performance in the Bench Press, Squat, and Deadlift — Journal of Strength and Conditioning Research (accessed 2026-09-02)
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