One Rep Max Calculator
Turn a set of 5-10 reps into your estimated 1RM using Epley and Brzycki formulas. Plan your percentages without hitting failure.
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Turn a set of 5-10 reps into your estimated 1RM using Epley and Brzycki formulas. Plan your percentages without hitting failure.
How to use One Rep Max Calculator
- Open the toolNo signup and nothing to install; it works as soon as the page loads.
- Set “Lifted weight”
- Set “Reps performed”
- Read the resultChange any input and the result is recalculated immediately.
Worked example with the defaults
- ESTIMATED 1RM (EPLEY) · 100 kg × 5 reps
- 117 kg
Nothing you enter leaves your device
All of the work happens inside your browser. Whatever you type is never packaged up and sent to a server, and no request this page makes carries it.
That makes it safe for contract amounts, personal details and internal documents you would rather not hand to a third party — close the tab and it is gone.
What this tool does not do
One Rep Max Calculator only does what a browser can do on its own — it talks to no backend service. So it keeps no history for you and syncs nothing across devices; if you need a record, copy or download the result.
It is also not a substitute for professional judgement. For legal, medical or tax decisions, treat the output as a starting point rather than a final answer.
Frequently Asked Questions
- Should I really test my 1RM?
- Most coaches recommend against true 1RM testing. Estimating from a submax set keeps joints and CNS happier and gives numbers within about 5%.