One-Rep Max Calculator
Estimate your one-rep max (1RM) using the Epley, Brzycki, and Lombardi formulas. Calculate your maximum lift capacity from submaximal weight and rep data without the risk of maximal testing.
Enter reps between 2 and 12
How This Calculator Works
Formula: Epley, Brzycki, and Lombardi Formulas
Three established formulas estimate 1RM from submaximal lifts. The Epley formula: 1RM = weight x (1 + reps/30). The Brzycki formula: 1RM = weight x (36 / (37 - reps)). The Lombardi formula: 1RM = weight x reps^0.10. All formulas take the weight lifted and the number of repetitions performed to estimate the maximum weight that could be lifted for a single repetition. Accuracy is highest when using sets of 3-10 reps.
Limitations
- Accuracy decreases significantly when using more than 10 reps — ideally use sets of 3-8 reps for estimation.
- The formulas assume good form is maintained throughout all repetitions.
- 1RM estimates vary between formulas, and different formulas may be more accurate for different exercises.
- Factors like fatigue, nutrition, sleep, and psychological state affect actual maximal performance.
These calculations are estimates based on established formulas. Individual results vary. Consult a healthcare professional before making significant changes to your diet or exercise routine.
The one-rep max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise with proper form. It is a fundamental metric in strength training, used to prescribe training intensities, track progress, and compare strength levels.
Directly testing your 1RM carries inherent risk, particularly for less experienced lifters. Heavy singles require excellent technique, adequate warm-up, and ideally a spotter. Estimating 1RM from submaximal lifts provides a safer alternative that is sufficiently accurate for most training purposes.
This calculator implements three widely used estimation formulas. The Epley formula is perhaps the most commonly used and works well across a range of rep counts. The Brzycki formula produces similar results and is particularly popular in the United States. The Lombardi formula uses a slightly different mathematical approach and can serve as a useful comparison point.
For the most accurate estimates, use a weight that you can lift for 3-8 repetitions with proper form. The set should be taken close to failure — you should feel that you could complete at most 1-2 more reps. Rep counts above 10 increasingly reduce the accuracy of all estimation formulas.
Once you know your estimated 1RM, you can use it to calculate training percentages. Common guidelines suggest training at 70-85% of 1RM for hypertrophy (muscle growth), 85-95% for maximal strength, and 50-70% for muscular endurance. This percentage-based approach provides a systematic framework for progressive training.