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One Rep Max Calculator

Estimate your 1RM using the Epley and Brzycki formulas. Enter your lift weight and reps to get started.

One Rep Max Calculator

Understanding Your One Rep Max

Your one rep max (1RM) is the heaviest weight you can lift for a single repetition with correct form. It's the most common benchmark for measuring absolute strength and serves as the foundation for percentage-based training programs used by powerlifters, Olympic lifters, and strength athletes worldwide.

Training Goal% of 1RMRep Range
Strength85–100%1–5 reps
Hypertrophy65–85%6–12 reps
Endurance50–65%12–20+ reps

The Formulas

The Epley formula (1RM = w x (1 + r/30)) is one of the most widely used prediction equations. The Brzycki formula (1RM = w x 36 / (37 - r)) is often preferred for lower rep ranges. Both assume reps are performed to failure or very close to it. Results are most accurate when reps are between 2 and 10 — beyond that, fatigue and technique breakdown reduce prediction reliability.

Tips for Better Estimates

Use a rep range of 3-5 for the best accuracy. Ensure each rep is performed with full range of motion and consistent tempo. Test after a proper warm-up but before fatigue from a full workout. Re-estimate every 4-6 weeks as your strength changes over time.

Disclaimer: This calculator is for informational purposes only and is not a substitute for professional coaching advice. Always use proper form and a spotter when lifting heavy weights.

Frequently Asked Questions

What is a one rep max (1RM)?
A one rep max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It is the gold standard for measuring maximal strength in a given exercise and is used by coaches and athletes to program training loads, track strength progress, and set training percentages.
How do the Epley and Brzycki formulas differ?
The Epley formula (1RM = weight x (1 + reps / 30)) tends to give slightly higher estimates, especially at higher rep ranges. The Brzycki formula (1RM = weight x 36 / (37 - reps)) is considered more accurate for lower rep ranges (under 10 reps). Both formulas are well-validated, and the difference between them is usually small when reps are kept below 10.
Is it safe to test my actual one rep max?
Testing a true 1RM carries higher injury risk than submaximal training. If you choose to test, always warm up thoroughly, use a spotter, and only attempt lifts with exercises you're experienced in. For most trainees, estimating 1RM from a 3-5 rep set using a calculator like this one is safer and nearly as accurate.
How should I use my 1RM for training?
Once you know your estimated 1RM, you can program training loads as percentages. For maximal strength, work at 85-100% of 1RM for 1-5 reps. For hypertrophy (muscle growth), use 65-85% for 6-12 reps. For muscular endurance, use 50-65% for 12-20+ reps. Recalculate your 1RM every 4-6 weeks as you get stronger.

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