One Rep Max Calculator

Why Estimate Instead of Test?

Actually testing your one rep max puts enormous stress on your joints, tendons, and central nervous system. For most lifters, estimating from a submaximal set is safer and accurate enough for programming. A well-executed set of 3-5 reps gives a reliable 1RM estimate within 5% of your actual max.

The 7 Formulas Explained

Each formula was developed from regression analysis on different populations and exercises:

• Epley (1985) — The most widely used formula. Linear relationship between weight and reps. Works well for moderate rep ranges (5-10).
• Brzycki (1993) — Most accurate for low rep ranges (1-10). Tends to give lower estimates than Epley at higher reps.
• Lander (1985) — Good general-purpose formula. Falls between Epley and Brzycki in most cases.
• Lombardi (1989) — Uses a power function. Tends to give more conservative estimates.
• Mayhew et al. (1992) — Developed and validated specifically with bench press data.
• O'Conner et al. (1989) — The simplest formula. Linear, easy to calculate mentally.
• Wathan (1994) — Exponential model. Considered accurate across a wide range of reps.

How to Use the Percentage Chart

The training load chart converts your 1RM into working weights for different rep ranges. This is how most strength programs are designed:

• 90-100% — Maximal strength (1-3 reps). Use sparingly — high CNS fatigue.
• 80-90% — Strength building (3-6 reps). The sweet spot for programs like 5/3/1.
• 70-80% — Hypertrophy (6-12 reps). Optimal for muscle growth.
• 60-70% — Muscular endurance (12-20 reps). Good for deload weeks and accessory work.

Accuracy Tips

For the most accurate estimate, use a set of 3-5 reps taken close to failure (1-2 reps in reserve). Sets above 10 reps become increasingly unreliable because muscular endurance, cardiovascular fitness, and pain tolerance start affecting the result more than pure strength.