What is the Epley formula?

The Epley formula estimates your one-rep max as: 1RM = weight × (1 + reps / 30). It was developed by Boyd Epley at the University of Nebraska in 1985 and remains one of the most widely cited 1RM prediction equations in strength and conditioning research.

How accurate is the Epley formula?

It is most accurate when the rep count is between 2 and 10. Accuracy drops for very high rep sets (above 15 reps) because fatigue and muscular endurance become significant factors. For best results, use a weight you can lift for 3–8 reps with good form.

Why does it say 1RM = weight when reps = 1?

When reps equals 1, the formula gives 1RM = weight × (1 + 1/30) ≈ weight × 1.033, a tiny 3.3% increase. This is expected — the Epley formula assumes the single rep you performed was not truly a maximal effort.

Should I actually attempt a one-rep max?

Not necessarily. Estimating 1RM from submaximal sets (3–8 reps) is safer for most athletes and reduces injury risk. Use the calculated 1RM for programming purposes rather than as a target to lift in every session.

How does Epley compare to Brzycki and other formulas?

The Epley formula tends to give slightly higher 1RM estimates than Brzycki at lower rep counts and slightly lower estimates at higher rep counts. Research suggests all common formulas perform similarly in the 2–10 rep range; the differences rarely exceed 5%.

One Rep Max Epley Calculator

Enter the weight and reps you performed to estimate your one-rep max using the Epley formula, plus a full percentage training table.

Enter Your Lift

Weight Lifted

Reps Performed (1 – 30)

Epley formula: 1RM = weight × (1 + reps / 30)

Enter your weight and reps, then click Calculate.

Estimated One-Rep Max (Epley)

Training Load Table

Working weights at common percentages of your 1RM

% 1RM	Weight	Approx Reps	Zone

Summary

The One Rep Max Epley Calculator uses the Epley formula — 1RM = weight × (1 + reps / 30) — to estimate the maximum weight you can lift for a single repetition. Developed by Boyd Epley in 1985, this formula is one of the most widely used methods for predicting strength from submaximal efforts. Input your working weight and rep count to get your estimated 1RM along with a complete training load table showing percentages from 50% to 95%.

How it works

Enter the weight you lifted in the Weight field.
Select your preferred unit — pounds (lb) or kilograms (kg).
Enter the number of reps you completed (between 1 and 30).
Click Calculate — the Epley formula (weight × (1 + reps / 30)) computes your estimated 1RM instantly.
Review the training percentage table to plan your working sets at 50–95% of your 1RM.

Use cases

Establish a baseline strength metric for a new training block.
Plan progressive overload percentages for powerlifting or Olympic lifting programs.
Track strength progress over time without maximal testing every session.
Set appropriate working weights for percentage-based programs like 5/3/1.
Compare estimated 1RM across different exercises to identify weak points.
Determine competition attempts in powerlifting or weightlifting meets.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu