What is a one-rep max (1RM)?

Your one-rep max is the heaviest weight you can lift for a single repetition with proper form. It's the standard benchmark for measuring maximal strength.

Why shouldn't I just test my 1RM directly?

Direct 1RM testing carries injury risk, especially for beginners. Estimating from a submaximal set (e.g., 5 reps) is safer and nearly as accurate.

How do I use my 1RM for training?

Training percentages are based on your 1RM: 70–85% for hypertrophy (muscle growth), 85–95% for strength, and 50–65% for muscular endurance.

Which 1RM formula is most accurate?

For reps under 10, Epley and Brzycki are the most widely validated. Our calculator averages six formulas to minimise error.

Does the exercise type matter?

Yes — 1RM formulas work best for compound barbell movements (bench press, squat, deadlift). Accuracy decreases for isolation exercises and machine movements.

One Rep Max Calculator — Estimate Your 1RM

Your one-rep max is estimated by plugging your lift weight and rep count into proven formulas. The average of six formulas gives the most reliable prediction.

Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition with good form. It is the standard benchmark for measuring strength and is used to program training percentages for hypertrophy, strength, and power cycles. Instead of risking injury with an actual maximal attempt, this calculator estimates your 1RM from a submaximal set using six peer-reviewed prediction equations, then averages them for a reliable estimate.

Lift Details

Exercise

Weight Lifted (kg)

Reps Completed

Most accurate for 1–10 reps

How to Use This Calculator

Select your exercise (bench press, squat, deadlift, overhead press, or other).
Enter the weight you lifted and the number of reps completed (2–20).
Click Calculate to see your estimated 1RM and a full training-percentage table.

Frequently Asked Questions

Methodology & Limitations

Formulas Used

**Epley:** 1RM = w × (1 + r/30). **Brzycki:** 1RM = w × 36/(37 − r). **Lombardi:** 1RM = w × r^0.10. **Mayhew:** 1RM = 100w / (52.2 + 41.9 × e^(−0.055r)). **O'Conner:** 1RM = w × (1 + r/40). **Wathan:** 1RM = 100w / (48.8 + 53.8 × e^(−0.075r)).

Limitations

Accuracy decreases for rep counts above 10. Formulas assume standard barbell exercises; they may not translate directly to machine exercises or unusual movement patterns. Individual leverages and training experience affect results.

Sources & Citations

Epley B. Poundage Chart. Boyd Epley Workout. 1985.
Brzycki M. Strength testing — predicting a one-rep max from reps-to-fatigue. J Phys Educ Recreat Dance. 1993;64(1):88-90.
LeSuer DA, et al. The accuracy of prediction equations for estimating 1-RM performance. J Strength Cond Res. 1997;11(4):211-213.

Last updated: 2026-02-12Reviewed by: PhysiqueLogic Editorial Team

Medical Disclaimer: This calculator provides estimates based on published formulas and is not a substitute for professional medical advice. Always consult a qualified healthcare provider before making changes to your diet or exercise routine.

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