A/B Testing Cloud Cost (Per-User) Calculator
Estimate the cloud cost per user of an A/B test and compare the test cost with serving all users through your control experience.
Overview
Use this A/B testing cloud cost calculator to estimate how much an experiment costs per exposed user. Enter your expected monthly users, test duration, traffic split, and the per-user cloud cost of both the control and variant to compare experiment spend with a control-only baseline.
How it works
The calculator estimates test exposure by multiplying monthly active users by the test duration divided by 30. It splits those users between the control and variant according to the variant traffic allocation, then applies each experience's per-user cloud cost. Fixed experiment costs are added to produce total test spend. The incremental cost compares that result with the estimated cost of serving every test user through the control experience.
How to use this calculator
- 1Enter the monthly active users for the feature or journey being tested.
- 2Set the number of days the experiment will run.
- 3Choose the percentage of users assigned to the variant.
- 4Add the estimated variable cloud cost per user for the control and variant.
- 5Include any fixed cloud costs created specifically for the test.
- 6Review the blended cost per user and the incremental cost versus control.
Example Calculation
Monthly active users
100000
Test duration
14
Variant traffic allocation
50%
Control cloud cost per user
$0
Variant cloud cost per user
$0
Fixed test cloud cost
$100
Blended cloud cost per user
$0.027
With about 46,667 estimated test users, total cloud cost is about 1,266.67, or 0.027 per user. That is about 333.33 more than serving the same users with the control only.
Frequently asked questions
What is cloud cost per user in an A/B test?
It is the average infrastructure cost associated with each user exposed to the experiment. It can include compute, database, storage, network, and experiment-platform usage when those costs are included in your inputs.
Why can an A/B test cost more than the control?
A variant may use more compute, make additional API calls, generate more logs, or need separate experiment tooling. Fixed setup and monitoring costs can also raise the cost of a short test.
How do I estimate the per-user cloud cost?
Use recent cloud billing and usage data where possible. Divide the variable cost associated with the relevant service or journey by its user count over the same period, then adjust for expected variant behavior.
Does a 50/50 traffic split always give the lowest cost?
No. A 50/50 split changes how many users receive each experience, but the lowest cost depends on the relative control and variant costs, fixed costs, and the traffic needed for a useful test.
What costs should I include as fixed test costs?
Consider experiment platform charges, dedicated environments, additional observability, data pipeline work, and temporary infrastructure that does not scale directly with the number of exposed users.
Why might actual cloud spend differ from this estimate?
Actual usage can vary with user behavior, caching, request size, retries, autoscaling, regional pricing, discounts, free allowances, and provider billing granularity.
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Assumptions and warnings
Assumptions
- Monthly active users are spread evenly across a 30-day month.
- Each exposed user creates one average unit of cloud usage represented by the selected per-user cost.
- Control and variant per-user costs include the relevant variable infrastructure usage you want to compare.
- Fixed test costs apply once for the selected test period.
- Results are planning estimates and exclude costs that are not entered, such as engineering time, vendor contracts, taxes, or committed-use discounts.
Warnings
- This calculator provides a cost estimate only and is not financial or procurement advice.
- Actual cloud spend can differ because of traffic patterns, caching, retries, free tiers, minimum commitments, and provider billing rules.