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A/B Testing File Size (Per-User) Calculator

Estimate compressed experiment data per participant, total A/B test file size, and the average data volume for each variant.

Your Details

Overview

This A/B Testing File Size (Per-User) Calculator estimates how much event data each experiment participant generates and the overall compressed file size. Enter your expected participants, variants, events per user, average event payload size, and expected compression reduction.

How it works

The calculator first multiplies average events per user by average event size to estimate raw data per participant. It then reduces that amount by the selected compression percentage. The compressed per-user amount is multiplied by the number of participants to estimate total file size, then divided by the number of variants to show an even-split average per variant.

How to use this calculator

  1. 1Enter the expected number of unique test participants.
  2. 2Add the total number of variants, including the control.
  3. 3Estimate how many tracked events each user will generate.
  4. 4Enter the typical uncompressed size of an event record in KB.
  5. 5Set the expected compression reduction and review the per-user and total estimates.

Example Calculation

Test participants

10000

Number of variants

2

Average events per user

12

Average event size

1.5

Compression reduction

40%

Estimated file size per user

10.80 KB

With 12 events per user at 1.5 KB each and 40% compression, each participant generates about 10.80 KB. The full test produces about 105.47 MB, or about 52.73 MB per variant with an even split.

Frequently asked questions

What is file size per user in an A/B test?

It is the estimated amount of experiment event data generated by one participant. It depends mainly on the number of events recorded, the average event payload size, and compression.

How is the total A/B test file size calculated?

The calculator multiplies compressed data per user by the number of participants, then converts the result from KB to MB.

Should I include the control as a variant?

Yes. For a standard A/B test, enter 2 variants: the control and one treatment. Include every treatment for A/B/n tests.

What compression reduction should I use?

Use a value based on your storage or export format if known. Compression can vary substantially with repeated fields, data format, and the type of event properties collected.

Why might actual file size differ from this estimate?

Actual size can change with event schemas, timestamps, user identifiers, null values, metadata, file format, compression method, and uneven participant allocation.

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Assumptions and warnings

Assumptions

  • Each participant generates the same average number of tracked events.
  • Average event size includes the fields and metadata stored with each event.
  • The compression reduction is applied uniformly to all event data.
  • Participants are split evenly across variants when estimating the average file size per variant.
  • Results are planning estimates and may differ from actual exported or stored file sizes.