Log Retention Storage Cost Calculator

Works out how much storage a log retention policy actually costs, at steady state, once compression is applied — the number worth knowing before someone sets retention to "keep everything forever, just in case" without checking what that actually costs.

Why "steady state" is the number that matters, not the daily rate

Logs don't disappear the day after they're written — they sit in storage for the full retention window before rolling off. That means the actual amount of data sitting in storage at any given moment, once the system has been running longer than the retention period, is daily volume × retention days, not just one day's worth. A 90-day retention policy at 50GB/day means roughly 4.5TB sitting in storage continuously, not 50GB — and that steady-state total, not the daily ingest rate, is what you're actually paying storage cost on every single month.

Compression is usually the biggest lever here, not retention length

Log data compresses extremely well — it's highly repetitive structured text, exactly the kind of data compression algorithms are best at. 5:1 to 10:1 compression ratios are common and realistic for typical application and access logs, and applying that ratio often saves more than trimming the retention window by weeks would. Before cutting retention short to save cost — which has real operational and compliance downsides — check whether compression is actually enabled and at what ratio, since that's frequently the cheaper, lower-risk lever to pull first.

Retention length is a compliance decision as much as a cost one

Shorter retention costs less, but plenty of retention requirements aren't actually a cost optimisation decision to make freely — PCI-DSS, HIPAA, SOC 2 and various industry or contractual requirements mandate specific minimum retention periods for certain log categories, and cutting below that minimum to save on storage isn't a tradeoff, it's a compliance gap. Know which regulatory or contractual floor applies to your specific logs before treating retention length as a pure cost lever.

What this calculator doesn't include

This covers storage cost only. Several log management platforms — Datadog, Splunk, and others — bill ingestion or indexing separately from storage, sometimes as the larger line item on the actual bill. If you're using a managed log platform rather than raw object storage, check its specific pricing model for ingestion and indexing costs on top of what's calculated here, since storage alone may understate the real total significantly.