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A/B Testing File Size Calculator

Estimate how a control and variant file size affect data transfer during an A/B test, including traffic allocation and cache hits.

Your Details

Overview

This A/B testing file size calculator estimates how much extra or reduced data transfer a variant may create compared with your control. Enter both file sizes, expected test traffic, average downloads, traffic split, and cache hit rate to model the likely transfer impact.

How it works

The calculator first estimates total file requests from visitors and average downloads per visitor. It removes the share expected to be served from cache, then allocates the remaining requests between control and variant according to the traffic split. It compares the resulting A/B test transfer with the transfer that would occur if every uncached request used the control file. A positive bandwidth difference means the test variant increases data transfer overall.

How to use this calculator

  1. 1Enter the downloaded file size for the control and variant in KB.
  2. 2Add the number of visitors expected to take part in the test.
  3. 3Enter the average number of file downloads per visitor.
  4. 4Set the percentage of traffic assigned to the variant.
  5. 5Add an estimated cache hit rate and review the bandwidth difference.

Example Calculation

Control file size

250

Variant file size

300

Test visitors

100000

Downloads per visitor

2

Variant traffic share

50%

Cache hit rate

30%

A/B test bandwidth difference

+/−3.34 GB

With 140,000 estimated uncached requests, a 50/50 test transfers about 3.34 GB more data than serving the 250 KB control file to every visitor.

Frequently asked questions

What does an A/B testing file size calculator measure?

It estimates the data transfer effect of serving a file-size variant to part of your test audience compared with serving the control to everyone.

What does a positive bandwidth difference mean?

A positive result means the selected A/B test allocation transfers more data than an all-control baseline. A negative result means it transfers less.

Why does the calculator ask for cache hit rate?

Cached requests may not download the file again, so only the uncached share is counted toward estimated file transfer.

Should I use compressed or uncompressed file size?

Use the typical transferred size seen by users, such as the compressed response size reported by your browser network tools or CDN analytics.

Does this calculator measure page speed?

No. It estimates file-transfer volume. File size can affect loading performance, but actual page speed also depends on network conditions, rendering, caching behavior, and other resources.

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Assumptions and warnings

Assumptions

  • File sizes are entered as downloaded kilobytes and are treated as constant for every request.
  • Each visitor is assumed to make the stated average number of file requests.
  • The cache hit rate is applied equally to control and variant requests.
  • One GB is calculated as 1,048,576 KB.
  • Results are transfer estimates and do not include HTTP headers, compression changes, retries, or other page assets.