Where does the fat-burn zone come from?

Mostly marketing. The 60-70% range burns a higher percentage of fat, but at higher intensities you burn more total calories, including more fat overall.

Target Heart Rate Calculator

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Age

Intensity

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Get the heart rate range that matches your chosen workout intensity. Plug it into your watch alert for consistent effort.

How to use Target Heart Rate Calculator

Open the toolNo signup and nothing to install; it works as soon as the page loads.
Set “Age”
Set “Intensity”
Read the resultChange any input and the result is recalculated immediately.

Worked example with the defaults

TARGET HEART RATE (BPM) · 70% of max HR (187 bpm): 131

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

Target Heart Rate 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

Where does the fat-burn zone come from?: Mostly marketing. The 60-70% range burns a higher percentage of fat, but at higher intensities you burn more total calories, including more fat overall.