One-Rep Max (1RM) & Strength Percentage Calculator
The problem: Direct 1RM testing with maximal barbell loads carries high injury risks for joints and connective tissue.
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One-Rep Max (1RM) & Strength Percentage Calculator: the complete guide
The One-Rep Max (1RM) and Strength Percentage Calculator estimates your maximum single-repetition lift capacity across major compound resistance exercises (bench press, squat, deadlift, overhead press) using the industry-standard Epley, Brzycki, and Lombardi formulas. Generate a complete strength percentage chart (50% to 95%) to precisely program your working sets, hypertrophy blocks, and strength peaking cycles without the injury risks of true maximal testing.
The Danger of Direct 1RM Testing vs. Submaximal Estimation
Testing an actual one-repetition maximum with maximal barbell loading places immense mechanical stress on tendons, ligaments, and the central nervous system. In untrained or intermediate lifters, technical breakdown under 100% intensity carries significant risks of acute muscle tears, spinal flexion, or joint sprains.
Submaximal estimation allows powerlifters, bodybuilders, and crossfitters to lift a safer weight for 3 to 10 clean repetitions and mathematically extrapolate their 1RM with 97%+ accuracy. This preserves joint health while providing the precise baseline required to calculate training percentages.
Comparing the Epley and Brzycki Scientific Formulas
The two most widely adopted formulas in exercise science are the Epley formula: 1RM = weight × (1 + reps / 30) and the Brzycki formula: 1RM = weight × (36 / (37 - reps)). The Epley equation is renowned for its accuracy in higher repetition ranges (5–10 reps), while Brzycki performs exceptionally well for heavy submaximal sets of 2 to 5 reps.
Our calculator displays the average of both formulas alongside a granular percentage breakdown table, showing your exact recommended poundage for 5x5 strength protocols (80–85%), 3x10 hypertrophy work (70–75%), and speed work (60%).
Step by step: how to use 1RM Calculator
- 1
Select your preferred weight unit (kg or lbs).
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Enter the weight lifted during your submaximal set.
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Input the number of clean repetitions completed before technical failure (best accuracy: 2 to 10 reps).
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View your estimated 1RM calculated via both Epley and Brzycki equations.
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Use the percentage matrix table to program your upcoming training sets at 60%, 70%, 80%, and 90% intensity.
Security & privacy
Strength formulas, lift records, and training percentage matrices are evaluated locally on your device without storing or uploading athletic data.