Question 1

What is one rep max (1RM)?

Accepted Answer

Your one rep max (1RM) is the maximum weight you can lift for a single repetition of an exercise with proper form. It is the standard measure of maximal strength in resistance training and is used to set training percentages — for example, working sets at 70–85% of 1RM for hypertrophy.

Question 2

How accurate is the one rep max calculator?

Accepted Answer

Our calculator uses the Epley formula: 1RM = weight × (1 + reps/30). It is most accurate when based on a lift of 1–10 reps. Beyond about 10 reps, the estimate becomes less reliable because muscular endurance begins to dominate over raw strength. For safety, never test a true 1RM without a spotter.

Question 3

Should I test my true 1RM?

Accepted Answer

Testing a true 1RM (lifting the heaviest weight possible for one rep) carries injury risk and requires a spotter. A safer approach is to lift a weight you can handle for 3–8 reps and use the calculator to estimate your 1RM. This is standard practice in most strength programmes.

Question 4

How do I use my 1RM in training?

Accepted Answer

Training programmes use percentages of 1RM to prescribe intensity. For strength, work at 85–95% of 1RM (1–5 reps). For hypertrophy (muscle growth), work at 67–85% (6–12 reps). For endurance, work below 67% (12+ reps). Always leave 1–3 reps "in the tank" to maintain form and avoid injury.

One Rep Max Calculator

Frequently Asked Questions