One Rep Max Calculator
Estimate your one rep max using Epley, Brzycki, Lombardi, and O'Conner formulas. Includes a training percentage chart.
For informational purposes only. Not a substitute for professional medical advice. Consult a healthcare provider before making changes to your diet or exercise routine.
About One Rep Max Calculator
Knowing your one rep max helps you programme your training with the right weights for your goals. This calculator uses four established strength formulas to estimate your 1RM from a submaximal set, so you can train smarter without the risk of maximal testing.
Four Formula Comparison
The calculator uses Epley, Brzycki, Lombardi, and O'Conner formulas. Each was developed from different research datasets. Seeing all four results plus their average gives you a more reliable estimate than any single formula. The visual comparison bars show how they stack up against each other.
Training Percentage Chart
Based on your estimated 1RM, the percentage chart tells you exactly what weight to use for different rep ranges and training goals. It covers everything from max strength (1-3 reps at 93-100%) to endurance (15-20 reps at 60-65%), making it a practical reference for any training programme.
Pairing with Nutrition
Strength training creates specific nutritional demands. Use the protein calculator to ensure you are eating enough protein for muscle recovery and growth. The calories burned calculator can estimate the energy cost of your weight training sessions.
Privacy
All calculations run in your browser. No workout data is sent or stored.
Frequently Asked Questions
What is a one rep max (1RM)?
Your one rep max is the maximum weight you can lift for a single repetition of a given exercise with proper form. It is a standard measure of maximal strength used in strength training programming to set training loads for different rep ranges.
Why use an estimate instead of testing directly?
Testing a true 1RM carries injury risk, requires a spotter, and needs proper technique at maximal loads. Estimating from a submaximal set (using a weight you can lift for multiple reps) is safer and provides a reliable enough number for training purposes.
Which formula is most accurate?
The Epley and Brzycki formulas are the most commonly used and tend to be the most accurate for rep ranges of 2 to 10. Accuracy decreases as rep count increases beyond 10. The calculator shows all four formulas plus their average to give you a reliable range.
How do I use the percentage chart?
The percentage chart shows what weight to use for different rep ranges based on your estimated 1RM. For example, if your 1RM is 100 kg, working at 80 percent (80 kg) for sets of 8 reps targets hypertrophy. Working at 90 percent (90 kg) for sets of 3 targets strength.
How often should I retest my 1RM?
Retesting every 4 to 8 weeks is common during a training programme. You do not need to test a true max. Simply perform a heavy set to near failure and plug the weight and reps into the calculator to get an updated estimate.