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Docker Registry Storage Calculator

Project storage needs for a private Docker registry from image count and retention.

About Docker Registry Storage Calculator

Registry storage is driven by: images × tags × avg_size, reduced by layer deduplication (shared base layers stored once). Formula: storage = images × tags × avgSize × (1 − layerSharing%). Aggressive tag retention policies and shared base images significantly reduce actual storage.

Formula

Registry Storage

storage = images × tags × avgSize × (1 − layerSharing%)

images
Number of distinct image repos
tags
Average retained tags per image
avgSize
Average compressed size
layerSharing%
Deduplication factor

Worked example

With the default values below, Docker Registry Storage Calculator returns Estimated Registry Storage of 70.3. Change any input above and every figure here is recalculated in your browser.

Inputs used

Distinct Imagesaccepts 1–100,000 images
30 images
Avg Tags Retainedaccepts 1–10,000 tags
20 tags
Avg Compressed Image Sizeaccepts 1–50,000 MB
200 MB
Layer Sharingaccepts 0–90 %
40 %

Results

Estimated Registry Storage
70.3 GB
Total Image Tags
600
Deduplication Savings
48,000 MB
Actual Storage
72,000 MB

Step by step

  1. 1Total tags= 600
  2. 2Naive storage (no sharing)= 117.2GB
  3. 3After deduplication= 70.3GB

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How does garbage collection affect storage?

Running registry garbage collection removes unreferenced blobs (layers no longer pointed to by any manifest), reclaiming space from deleted tags — without GC, deleted tags still occupy disk.

What's a good retention policy?

Keep the last N tags per image (e.g. 10-20) plus any tags matching production release patterns; aggressively prune development/feature-branch tags older than a few days.

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