Training
One-Rep Max Calculator
Estimate your one-rep max from load and repetitions. Compare established methods or analyse sets with RIR/RPE.
Context
- An e1RM is usually an estimate, not a performance promise.
- Higher repetitions and RIR/RPE increase uncertainty.
- Results can vary by exercise and person.
Frequently asked questions
What is a 1RM?
A 1RM is the load for one controlled maximal repetition. This calculator can estimate it from other sets.
How is the 1RM estimated?
The engine calculates seven established formulas and uses their median as the consensus value.
Why do formulas differ?
Methods weigh repetitions differently. The method range makes those differences visible.
How many reps are suitable?
Lower repetition counts usually provide a more stable basis; higher reps remain available with an explicit uncertainty note.
What do RIR and RPE mean?
RIR estimates repetitions in reserve. RPE describes perceived proximity to the limit and is mapped to an RIR approximation.
Do I need to test my true 1RM?
No. The calculator does not ask you to perform a direct maximum attempt.
Why can multiple sets differ?
Different loads, repetitions and effort inputs can produce different estimates.