Health and fitness tools
One Rep Max Calculator
Estimate your one-rep max from weight lifted and reps completed using Epley and Brzycki formulas locally in your browser.
Enter the weight you lifted and how many reps you completed with good form (1-12 reps). The calculator averages the Epley and Brzycki formulas and shows training percentages from that estimate. Use the same weight unit for input and result. This is a general fitness estimate, not medical advice; lift within your ability and use a spotter for heavy attempts. The calculation runs locally in your browser; your values are not uploaded or stored.
Estimate your max lift from a submaximal set.
Enter the weight you lifted and the reps you completed with good form (1-12 reps). The calculator averages the Epley and Brzycki estimates and shows training percentages from that max. The result uses the same weight unit you entered. This is a general fitness estimate, not medical advice; your values are calculated locally and are not uploaded or stored.
Frequently Asked Questions
Everything you need to know about this tool, how it works, and privacy.
How does the one rep max calculator work?
Enter the weight you lifted and the reps you completed with good form (1-12 reps). The calculator computes the Epley estimate as weight x (1 + reps / 30) and the Brzycki estimate as weight x 36 / (37 - reps), then averages the two for the estimated one-rep max. For example, 100 for 5 reps gives Epley 116.7, Brzycki 112.5, and an average of about 114.6.
What training percentages does it show?
It shows 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, and 50% of the estimated max in the same unit you entered, so you can pick working weights for strength, hypertrophy, or warm-up sets.
Which inputs are accepted?
Enter a weight between 0.5 and 1000 in the unit you train with and whole-number reps between 1 and 12. For 1 rep the estimate equals the weight lifted. Missing values, zero, negative numbers, non-numeric text, fractional reps, and values outside these ranges show a clear error instead of a result.
Is this a guarantee of what I can lift?
No. Epley and Brzycki formulas are general estimates that are most reliable for low-to-moderate rep sets; your actual max can differ with exercise, technique, fatigue, training history, and safety equipment. Lift within your ability, use a spotter for heavy attempts, and consult a qualified coach or healthcare professional for personal training advice. This estimate is not medical advice.
Do my values leave my browser?
No. The calculation and copy action run locally in your browser. CodeASystem does not upload or store the weight or reps you enter.