What is your one-rep max?

Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition of an exercise with good form. It is the standard benchmark of strength and the reference point most training programmes use to set working weights. Rather than risk injury testing a true max, this calculator estimates your 1RM from a set you have already completed.

How the estimate works

The calculator uses the Epley formula: 1RM = weight × (1 + reps ÷ 30). It then builds a percentage table so you can see suggested weights for different rep ranges — useful for planning sets at 80% for strength or 70% for hypertrophy. The estimate is most accurate when your set used between 1 and 10 reps; beyond that, fatigue makes predictions less reliable.

How to use your 1RM in training

Strength work typically uses 85–95% of 1RM for low reps, while muscle-building work sits around 67–80% for moderate reps. Knowing your 1RM lets you pick the right weight without guessing. Recalculate every few weeks as you get stronger, and always prioritise good technique over heavier numbers.

Frequently asked questions

Is it safe to test my actual 1RM?

True max attempts carry a higher injury risk and should only be done by experienced lifters with a spotter and a proper warm-up. For most people, an estimate from a 3–5 rep set is safer and accurate enough.

Why do different calculators give different numbers?

There are several formulas (Epley, Brzycki, Lombardi) that weight reps slightly differently. They all give similar results for low rep counts.

Disclaimer: This calculator provides estimates for informational purposes only. Lift within your ability and consult a qualified coach or professional where appropriate.