One Rep Max Calculator

What is a one rep max?

Your one rep max (1RM) is the heaviest weight you can lift for one full repetition with good form. Strength programmes use it to set training weights: for example, 75% of your 1RM for sets of 8–10 reps to build muscle.

Why estimate instead of testing?

Testing a true 1RM is tiring and carries more injury risk, especially without a spotter or coaching. Estimating it from a heavier set of 3–10 reps is safer and accurate enough for planning. This calculator runs seven well-known formulas (Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner and Wathan) and shows the range, so you can see how consistent they are.

Getting an accurate estimate

• Use a set of 3–6 reps taken close to failure with good form. Estimates get less reliable above 10 reps.
• Warm up properly first, and use a spotter or safety pins for bench press and squats.
• Recalculate every 4–6 weeks as you get stronger.

Using the training zones

The zones and rep table turn your 1RM into working weights: heavy low-rep work for strength, moderate weights for muscle growth, and lighter sets for endurance. The progressive overload plan then adds weight gradually over the weeks. Consistency and good technique matter more than hitting every number exactly.