A/B Testing API Cost (Per-User) Calculator
Estimate the API cost of running an A/B test, including total monthly spend and the cost per user exposed to the test.
Overview
Use this A/B Testing API Cost (Per-User) Calculator to estimate the monthly cost of experiment-related API usage. Enter your monthly users, the share included in the test, expected API calls per tested user, API price, and any fixed platform fee.
How it works
The calculator first estimates the number of users exposed to the test by multiplying monthly active users by the selected traffic percentage. It then multiplies that audience by the average calls per user to estimate call volume. Usage cost is calculated from the price per 1,000 calls, then any fixed monthly platform fee is added. The total is divided by tested users to show the per-user test cost.
How to use this calculator
- 1Enter your expected monthly active users.
- 2Set the percentage of users who will be included in the A/B test.
- 3Estimate the average experiment-related API calls made by each tested user.
- 4Enter the API provider's cost per 1,000 calls.
- 5Add any monthly platform fee and review the cost per tested user.
Example Calculation
Monthly active users
100000
Traffic included in test
50%
API calls per tested user
20
API cost per 1,000 calls
$2
Monthly platform fee
$100
Cost per tested user
$0.0420
With 50,000 users in the test and 1,000,000 API calls, usage costs are $2,000. Adding a $100 platform fee gives a total monthly cost of $2,100, or $0.0420 per tested user.
Frequently asked questions
What is API cost per tested user?
It is the total estimated monthly cost of the A/B test divided by the number of users exposed to that test during the month.
Should I use all users or only users in the experiment?
Use all monthly active users as the starting audience, then set the traffic percentage that will actually be exposed to the A/B test.
Do A/B test variants increase API calls?
Not necessarily. If every exposed user makes one evaluation regardless of variant, calls per user may stay the same. Increase the calls-per-user estimate if your implementation makes additional requests for variants, analytics, or events.
What should be included in API calls per user?
Include experiment assignment, feature flag checks, event tracking, metrics retrieval, and other API requests that are directly caused by the test.
Why is the cost per active user lower than the cost per tested user?
Cost per active user spreads the full test cost across everyone active that month, including people who were not included in the experiment.
Does this include free API tiers or volume discounts?
No. Enter an effective cost per 1,000 calls that already reflects any expected credits, free-tier allowance, or volume discount.
Explore Related Calculators
Assumptions and warnings
Assumptions
- Each tested user generates the stated average number of experiment-related API calls during the month.
- The API provider charges a consistent rate per 1,000 calls with no volume discounts, free-tier credits, or overage changes.
- The fixed platform fee is fully allocated to this one A/B test.
- Users outside the selected test traffic percentage do not generate experiment-related API calls in this estimate.
Warnings
- This calculator provides a planning estimate only; actual API bills can differ because of billing rules, retries, caching, free tiers, taxes, and usage patterns.
- Check your provider's current pricing and billing units before committing to a testing budget.