What is a 1RM?
Your one-rep max (1RM) is the heaviest weight you can lift for a single complete repetition with proper form. Since maxing out on a lift like the bench press carries injury risk and requires a spotter, lifters typically estimate their 1RM from a lighter set taken to or near failure instead.
The formula
This calculator uses the Epley formula, one of the most widely used 1RM estimation methods: 1RM = Weight × (1 + Reps ÷ 30). For example, bench pressing 80 kg for 5 reps estimates a 1RM of roughly 93 kg. The calculator also shows common training percentages of your estimated max (90%, 80%, and 70%), which are frequently used to structure strength or hypertrophy training blocks.
Rep-max formulas are most accurate for sets of about 1-10 reps taken close to failure; estimates get progressively less reliable for higher rep counts, and individual technique, fatigue, and muscle fiber type all affect real-world accuracy.
For general training planning purposes only.