112.5
kg
116.7
kg
113.7
kg
114.3
kg
108.6
kg
102.9
kg
91.4
kg
80
kg
112.5
kg
116.7
kg
113.7
kg
114.3
kg
108.6
kg
102.9
kg
91.4
kg
80
kg
The One Rep Max (1RM) is the maximum weight an individual can lift for a single repetition with proper form. It is the gold standard measurement of maximal strength and serves as the foundation for designing resistance training programs, tracking progress, and comparing strength levels across individuals. This One Rep Max Calculator uses three validated prediction formulas — Brzycki, Epley, and Lander — to estimate your 1RM from a submaximal lift, eliminating the risk and difficulty of actual maximal testing.
Directly testing a true 1RM requires extensive warm-up, proper spotting, and carries inherent injury risk, especially for novice lifters. Prediction equations allow athletes and coaches to estimate maximal strength from sets of multiple repetitions, typically using loads that allow 2-10 reps. The accuracy of these predictions is highest when using lower rep ranges (3-5 reps) and decreases as the rep count increases beyond 10, because the relationship between reps and percentage of 1RM becomes less predictable at higher rep ranges.
The Brzycki formula, published in 1993, is widely considered the most accurate for rep ranges of 1-10 and is the most commonly used equation in strength training literature. The Epley formula is simpler and tends to give slightly higher estimates, particularly at higher rep ranges. The Lander formula provides an intermediate estimate. By averaging all three, this calculator gives a robust prediction that accounts for the inherent uncertainty in any single formula.
Once your estimated 1RM is established, the calculator provides training load percentages. The percentage-based approach to programming is fundamental to periodized strength training: 95% of 1RM corresponds to approximately 2 reps (maximal strength), 90% to 3-4 reps (strength-focused), 80% to 7-8 reps (hypertrophy-strength blend), and 70% to 11-12 reps (hypertrophy-endurance). These percentages guide exercise prescription for specific training goals.
For accurate predictions, perform your test set with a weight you can lift with perfect form for the desired number of reps, taken to within 1-2 reps of failure. Rest fully (3-5 minutes) before the test set. Test sets of 3-5 reps provide the most accurate 1RM predictions. Update your estimated 1RM every 4-8 weeks as strength improves. This calculator is applicable to all barbell and machine exercises, though accuracy is highest for compound movements like squats, bench press, deadlift, and overhead press.
Brzycki (1993): 1RM = Weight x 36 / (37 - Reps). Epley: 1RM = Weight x (1 + Reps/30). Lander: 1RM = Weight x 100 / (101.3 - 2.67123 x Reps). Average 1RM = mean of all three formulas. Training percentages are calculated from the average 1RM.
Use the average 1RM for programming. If formulae differ by more than 5%, your rep count may be outside the accurate prediction range (ideally 3-7 reps). The training percentages show approximate weights for different rep ranges. Use 90-95% for strength sets (1-3 reps), 75-85% for hypertrophy (6-12 reps), and 65-75% for endurance (12-20 reps). Retest every 4-8 weeks.
Inputs
Results
100 kg for 5 reps estimates a 1RM of approximately 114.5 kg.
Inputs
Results
140 kg for 3 reps estimates a 1RM of approximately 150.6 kg.
The Brzycki formula is generally most accurate for 1-10 reps. All formulas lose accuracy above 10 reps. Using the average of multiple formulas provides the best estimate. For maximum accuracy, use a test set of 3-5 reps.
Test sets of 3-5 reps provide the most accurate predictions. Sets of 1-2 reps are very close to actual 1RM. Beyond 10 reps, accuracy decreases significantly because fatigue and muscular endurance become larger factors.
1RM testing carries higher injury risk than submaximal testing. If you do test, warm up thoroughly, use a spotter, ensure proper form, and attempt single-rep increases of 2-5% until failure. Beginners should use prediction equations instead.
Every 4-8 weeks during a structured training program. More frequent testing disrupts training and does not allow sufficient time for measurable strength gains. Use the predictions to guide training between tests.
They work best for barbell compound movements (squat, bench, deadlift, overhead press). They are less accurate for isolation exercises, machine exercises, and movements where technique is a major limiting factor (Olympic lifts).
Training max is typically set at 85-90% of your estimated 1RM to provide a buffer for daily variation in strength. Programs like 5/3/1 use a training max to ensure consistent progression without frequent maximal attempts.
Each formula was derived from different populations and statistical methods. Brzycki uses a linear model, Epley uses a ratio model, and Lander uses a polynomial model. The differences are usually within 5% and averaging provides the best estimate.
For prediction accuracy, your test set should be performed to technical failure (point where form breaks down) or 1-2 reps shy of failure. Absolute muscular failure increases injury risk and is not necessary for accurate predictions.
Select your training goal: Strength (85-95%, 1-5 reps), Hypertrophy (67-85%, 6-12 reps), Endurance (50-67%, 15-25 reps). Multiply your estimated 1RM by the percentage to get your working weight.
Bodyweight itself does not affect formula accuracy, but relative strength (1RM / bodyweight) is a better comparison metric across different body sizes. A 100 kg bench press at 70 kg bodyweight (1.43 ratio) is more impressive than at 100 kg bodyweight (1.0 ratio).
Roboculator Team
The Roboculator Team explains calculations, planning tools, and practical formulas in clear language for real-life situations.
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