One Rep Max Calculator
Estimate your one-rep max from weight lifted and reps using five proven formulas
Strength
Fitness
Weightlifting
Training
About This Tool
This One Rep Max Calculator estimates your maximum strength using five well-established formulas and averages them for a balanced result.
- Epley — A widely used formula based on linear regression of submaximal reps.
- Brzycki — Popular in academic research, most accurate for reps ≤ 10.
- Lombardi — Uses a power curve relationship between reps and load.
- O'Conner — A simplified linear formula with a different slope coefficient.
- Wathan — An exponential decay model providing smooth, natural estimates.
For best results, use a weight you can lift for 1–10 reps with good form. Pair this tool with our Protein Intake Calculator, Macronutrient Calculator, and Lean Body Mass Calculator to optimize your nutrition and body composition for strength training.
All processing happens entirely in your browser — no weight or rep data is sent to any server.
Frequently Asked Questions (FAQ)
What is a one-rep max (1RM)?
A one-rep max is the maximum amount of weight you can lift for a single repetition of a given exercise with proper form. Knowing your 1RM helps you plan training loads at specific intensity percentages for strength, hypertrophy, and endurance goals.
How accurate is this calculator?
This calculator uses five well-established formulas (Epley, Brzycki, Lombardi, O’Conner, and Wathan) and averages their results for a balanced estimate. The formulas are most accurate when the input reps are between 1 and 10. For higher reps, the estimates become less precise. Use the result as a guideline—actual 1RM should be tested under proper supervision.
Why are multiple formulas used and averaged?
Each formula was developed from different studies and populations, so they produce slightly different results. Averaging minimizes the bias of any single formula and gives a more reliable estimate. You can see each formula’s individual result in the comparison table for transparency.
Can I use this for any exercise?
Yes! The formulas work for any strength exercise where you can count repetitions: bench press, squat, deadlift, bicep curl, overhead press, and more. The key is to use a challenging weight where the rep count represents a true set taken to or near failure with good form.
How should I use the training percentage table?
Use 85–100% for strength and power, 65–80% for hypertrophy (muscle growth), and 50–60% for muscular endurance. Pair this tool with our Protein Intake Calculator and Macronutrient Calculator to align your nutrition with your training goals.
Is my data safe?
Yes. All calculations happen entirely in your browser. No weight or rep data is ever sent to a server. Check out our Body Fat Percentage Calculator and Lean Body Mass Calculator for more private fitness tracking tools.