Choose a lift.
Use the weight and reps from one successful set of a single exercise.
Free training tool
Estimate your one-rep max.
Find an estimated 1RM from the weight and reps you completed.
Use it to put a number on a strong set, compare your progress over time, or plan your next training block. No account required.
Epley formula
Estimate your one-rep max.
Enter a successful set. This estimate is most useful for sets of 1 to 10 reps.
Estimated 1RM
116.7 kg
Based on 100 kg for 5 reps.
How to use it
Use a real set, not a guess.
Enter the details.
Select the unit you used, then add the load and the completed reps.
Treat it as a guide.
Compare estimates across similar sets over time instead of chasing one number.
The calculation
A useful estimate, not a promise.
This page uses the Epley formula: weight × (1 + reps ÷ 30). It is a practical way to turn a multi-rep set into a benchmark you can track.
Estimates become less dependable when sets are very high rep, technique changes, or fatigue is unusually high. Use good judgement and stop if something hurts.
Example
100 kg × 5 reps
Estimated with Epley
116.7 kg
A different rep range may produce a different estimate. Consistency is more useful than perfection.
Keep the context
Your strongest set is part of a bigger picture.
Bask keeps your workouts, training history, and personal records in one place. It can recognise estimated 1RM PRs from the sets you log, then help with what to train next.
Download on the App Store
Free to download. iPhone, iOS 15 or later.
From set to progress
- 01Log the work you actually completed.
- 02See estimated PRs as your training develops.
- 03Let Kai help make the next exercise fit the session.
FAQ
1RM calculator questions
What is a one-rep max?
Your one-rep max, or 1RM, is the heaviest weight you could lift once for a particular exercise with good technique. A calculator estimates it from a multi-rep set, so you do not have to test a maximal lift.
How does this 1RM calculator work?
This calculator uses the Epley formula: weight multiplied by one plus reps divided by 30. It uses the weight and reps from a successful set to estimate what one hard repetition may be worth.
How accurate is an estimated 1RM?
It is an estimate, not a guarantee. It is generally more useful for moderate-to-heavy sets, especially around 1 to 10 reps. Exercise selection, technique, fatigue, and your own strengths can change the result.
Should I test my actual one-rep max?
Only if you know how to do so safely and it makes sense for your training. A calculated estimate can be a useful way to track progress without regularly attempting maximal lifts.
Can I use this calculator in pounds?
Yes. Choose kilograms or pounds before calculating. The estimate stays in the same unit as the weight you entered.