1RM Calculator - One Rep Max

Calculate your one rep max using the Epley formula. Free online 1RM calculator for weightlifting with formula, examples, and FAQ.

Weight Lifted (kg)

Reps Performed

How It Works

The One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. Knowing your 1RM is essential for programming strength training, as training percentages are based on it. The Epley formula provides a reliable estimate without needing to test your actual maximum, which can be risky.

Formula

1RM = Weight × (1 + Reps / 30) — Epley Formula

The Epley formula estimates your one rep max based on the weight you lifted and the number of repetitions performed. It assumes that each additional rep represents approximately 1/30th of the weight as decreased intensity. This formula works best for reps between 1-10 and becomes less accurate for higher rep ranges.

Examples

Input	Output
80 kg × 5 reps	1RM: 93.3 kg
100 kg × 3 reps	1RM: 110.0 kg
60 kg × 10 reps	1RM: 80.0 kg

Frequently Asked Questions

How accurate is the Epley formula?▾

The Epley formula is most accurate for 1-10 repetitions and tends to overestimate for higher rep ranges. For the best estimate, use a weight that allows 3-5 reps. The formula is generally accurate within 2-5% of actual 1RM for compound exercises like squat, bench press, and deadlift.

Should I test my actual 1RM?▾

Testing actual 1RM carries injury risk, especially for beginners. Using the Epley formula with a 3-5 rep max provides a safe and reasonably accurate estimate. If you do test 1RM, always use a spotter, warm up thoroughly, and follow proper progression.

What are training percentages used for?▾

Training percentages guide workout intensity: 90-100% for maximal strength (1-3 reps), 80-90% for strength (3-6 reps), 70-80% for hypertrophy (6-12 reps), and 60-70% for endurance (12+ reps). Most training programs cycle through these ranges.