A/B Testing API Cost Per-User Calculator FAQ
Answers to common questions about estimating A/B test API cost, traffic allocation, call volume, and per-user results.
Use these answers to understand the calculator inputs, the monthly cost estimates it produces, and the assumptions that can affect real-world API bills.
General calculator questions
Basic questions about the purpose and outputs of the calculator.
What does the A/B Testing API Cost Per-User Calculator estimate?
It estimates monthly experiment-related API spend, users exposed to the test, API call volume, cost per tested user, and cost per active user.
Who is a tested user?
A tested user is a monthly active user included in the selected share of traffic for the experiment.
What is total monthly test cost?
It is usage-based API cost plus the monthly platform fee entered for the test.
Is the result a confirmed provider bill?
No. It is a planning estimate based on the inputs and may differ from actual billing.
Inputs and call volume
How to select the audience, calls-per-user, and pricing inputs.
Should monthly active users include users outside the experiment?
Yes. Enter the total monthly active-user audience, then use test traffic to identify the exposed share.
What belongs in API calls per tested user?
Include experiment-related calls such as assignment, flag evaluation, exposure logging, analytics events, or metrics requests when they are part of the cost you want to estimate.
Should I count every product API call?
No. Count only calls attributable to the experiment unless the purpose is to estimate a broader platform cost.
What API price should I enter?
Enter the provider's effective charge per 1,000 calls for the expected usage period. Review current provider pricing separately.
How do I include a free tier or discount?
Use an effective per-1,000-call rate that reflects the expected benefit, or calculate a separate scenario after accounting for the allowance.
Understanding the results
How the main outputs differ and when each is useful.
Why is cost per active user lower than cost per tested user?
It allocates the same total test cost across all monthly active users, including people not exposed to the experiment.
Can cost per tested user decrease as traffic increases?
Yes. A fixed fee is shared across more tested users, although changes in pricing tiers or call behavior can alter the result.
What happens if API calls per user double?
The usage-based portion of total cost doubles, assuming the rate per 1,000 calls remains constant.
Does a 50/50 A/B test mean every user creates twice as many calls?
Not necessarily. A user generally sees one assigned variant. Extra calls occur only if the implementation makes additional requests, events, or evaluations.
Accuracy and planning use
Assumptions and factors that can make actual costs different.
What can make actual API costs different from the estimate?
Retries, caching, batching, failed calls, free tiers, volume pricing, minimum charges, taxes, and changing user activity can all affect billed cost.
Does the calculator include statistical significance costs?
No. It estimates operational API and platform cost, not sample-size requirements, analyst time, or the opportunity cost of an experiment.
Can I compare two experiment designs with this calculator?
Yes. Keep the pricing basis consistent, then compare traffic share, calls per user, fixed fees, total monthly cost, and per-tested-user cost.
Should I allocate the entire platform fee to one test?
Only if that reflects your planning approach. If multiple tests share a platform, allocating a portion to each test may be more representative.
What is API cost per tested user?
It is total estimated monthly A/B test cost divided by the users exposed to that test during the month.
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