> For the complete documentation index, see [llms.txt](https://docs.tryterra.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tryterra.co/faq/help-topics/data-api-sdk/webhooks-dedup-and-sync-reliability/hrv-app-vs-api-calculation-diff.md).

# Why does Oura app HRV differ from the API HRV?

A different HRV in the provider's app versus the Terra API is usually a **difference in calculation method, not a data discrepancy**.

* Terra computes an arithmetic mean across all per-sample HRV readings for the sleep period (`avg_hrv_rmssd`).
* The provider app often displays its own internally pre-calculated average.

Both numbers reflect the same underlying samples, just aggregated differently. Provide the specific night's date to match values precisely.


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