What Is One-Rep Max and Why It Matters
Your one-rep max is the maximum weight you can lift for a single repetition of a given exercise. It serves as the foundation for percentage-based strength programming. Coaches and athletes use 1RM values to prescribe training loads that target specific adaptations; hypertrophy, strength, or power. Knowing your 1RM eliminates guesswork and ensures every set is performed at the right intensity for your goals.
The Five Formulas Explained
This calculator uses Brzycki, Epley, Lander, Lombardi, and O'Conner formulas. Each takes your weight lifted and reps performed as inputs but applies different mathematical models. Brzycki uses a linear model accurate for low reps. Epley adds a fraction of the reps to a multiplier. Lander, Lombardi, and O'Conner each apply slightly different regression curves derived from experimental data.
How to Use Training Percentages
The training load table converts your 1RM into working weights at various percentages. Training at 50-65% develops muscular endurance. The 70-80% range builds hypertrophy. Working at 85-95% develops maximal strength. Percentages above 95% are reserved for peaking phases before competition. Always warm up progressively and use appropriate rest periods between heavy sets.
Safety and Best Practices
Estimating your 1RM from submaximal sets is safer than performing a true max attempt. Always use a spotter or safety pins for heavy lifts. Warm up thoroughly before testing; start with the bar and increase in 10-20% jumps. If your estimated 1RM changes significantly between sessions, verify your rep counts are accurate and that you are reaching true failure on your test sets.
