One Rep Max Calculator
Free one rep max (1RM) calculator. Estimate your max lift from weight and reps using Epley, Brzycki, Lombardi, Mayhew, O'Conner, and Wathen formulas.
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What is One Rep Max Calculator?
The One Rep Max Calculator estimates the maximum weight you can lift for a single repetition (1RM) based on a submaximal set. Instead of risking a true max-out attempt, you enter the weight and reps of a working set and the tool applies six validated formulas — Epley, Brzycki, Lombardi, Mayhew et al., O'Conner et al., and Wathen et al. — to give you a safe, science-based estimate. It also generates a percentage-based training chart for programming your lifts.
Key Benefits
- Avoid the injury risk of testing a true 1RM by estimating from a lighter set
- Get six formula estimates at once to see the full range of your potential max
- Plan percentage-based training programs (5/3/1, Prilepin's table, NSCA) with accurate loads
- Track strength progress over time without frequent max-out sessions
- Works for every barbell and dumbbell exercise
Common Use Cases
- •Strength athletes calculating loads for periodized programs
- •Coaches assigning training percentages to clients safely
- •Fitness enthusiasts tracking progress without maxing out
- •Powerlifters preparing for meet attempts using formula averages
- •Gym-goers finding the right starting weight for a new program
How to Use the One Rep Max Calculator
- Enter weight: Type the weight you lifted in kilograms (or pounds, consistently).
- Enter reps: Type how many reps you performed with that weight (1-15 for best accuracy).
- Pick a formula: Select a primary formula — Epley is a good default for most lifters.
- Review results: Read your estimated 1RM, compare all six formulas, and use the percentage chart to plan training loads.
Key Features
- Six validated 1RM formulas: Epley, Brzycki, Lombardi, Mayhew et al., O'Conner et al., and Wathen et al.
- Side-by-side formula comparison table so you can see the full range of estimates.
- Auto-generated 50-100% training percentage chart for programming loads.
- Input validation caps reps at 1-15 for formula accuracy and rejects invalid weights.
- One-click copy of your 1RM result for training logs and spreadsheets.
- 100% client-side — no sign-up, no server calls, works offline.
Frequently Asked Questions
Which 1RM formula should I use?
Epley and Brzycki are the most widely used and validated. Epley tends to be more accurate for moderate rep ranges (5-10), while Brzycki works better for lower reps (1-5). If you are unsure, use the average of several formulas as a reasonable estimate.
How accurate are 1RM estimates?
Most formulas are accurate within about 5-15% for rep ranges of 1-10. Accuracy decreases for higher rep counts (above 10) because fatigue from cardiovascular and muscular endurance factors becomes significant. For the most reliable estimate, use a weight you can lift for 3-6 reps.
Should I test my actual 1RM instead?
Testing a true 1RM carries injury risk, especially for beginners or those without a spotter. Estimating from a submaximal set is safer and sufficient for most training purposes. Only advanced lifters preparing for a competition should test true 1RM, and always with proper spotting and form.
How do I use the percentage chart?
The chart shows training loads at 50-100% of your estimated 1RM. For pure strength, work at 85-100%. For hypertrophy (muscle growth), use 65-80%. For muscular endurance, train at 50-65%. These ranges align with common programs like 5/3/1, Prilepin's table, and NSCA guidelines.