Free Calculator

1RM Calculator

Calculate your one rep max for any exercise. Enter your weight and reps — get your estimated 1RM from five different formulas instantly.

What is a 1RM and why does it matter?

Your one rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. It is the gold standard for measuring maximal strength and the foundation for designing effective training programs.

Most evidence-based strength programs use percentages of your 1RM to prescribe training loads. Strength work typically uses 80–90% of 1RM, hypertrophy training 65–80%, and muscular endurance 50–65%. Without knowing your 1RM, programming becomes guesswork.

A calculated 1RM is a safe and practical way to estimate your maximum strength without the risks of a direct max test. Our calculator uses five established formulas — Epley, Brzycki, Lander, Lombardi and O'Conner — and averages the results for the most accurate estimate possible.

How to use the 1RM calculator

Using the calculator is simple. Perform a set with a weight you can lift for 2–10 reps — this is the most accurate range. Enter the weight you lifted and the number of reps completed, then click Calculate. The calculator instantly gives you your estimated 1RM from all five formulas.

The rep range table below the result shows you the estimated weights for every major rep range from 1 to 20 reps. Use this to set your training weights across the full rep spectrum.

Which 1RM formula should I use?

The Epley formula is the most widely used and works well across most rep ranges. The Brzycki formula is excellent for lower rep ranges (1–6 reps) and is popular in powerlifting. For best results, use the average of all five formulas — which is exactly what our calculator shows.

Individual variation means no single formula is universally best. Factors like muscle fiber composition, body segment lengths and training experience all influence how your actual 1RM compares to the estimate. The average of multiple formulas consistently outperforms any single formula.

Frequently asked questions

1RM (one-rep max) is the maximum weight you can lift for a single repetition with proper form. It is the most common way to measure maximum strength in exercises like bench press, squat and deadlift.
The estimate is most accurate in the 1–6 rep range (±5%). At 7–10 reps accuracy is good (±8%). Above 10 reps accuracy decreases significantly, as fatigue becomes a bigger factor than pure strength.
Epley and Brzycki are the most researched and widely used formulas. Epley works better at higher rep ranges, Brzycki at lower. Our calculator shows all five formulas and their average for maximum accuracy.
A real 1RM test is more accurate but requires good technique, proper warm-up and ideally a spotter. For beginners a calculated estimate is safer. For intermediate and advanced lifters, testing directly every few months is worthwhile.
Most evidence-based training programs use percentages of your 1RM. Strength training typically uses 80–90% of 1RM, hypertrophy training 65–80%, and endurance training 50–65%. Knowing your 1RM lets you program precisely.
An estimated 1RM is calculated from a submaximal set using a mathematical formula. An actual 1RM is tested directly. The estimate is safe and practical for everyday training, while the actual test gives the most precise number.
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