How many ad creatives to launch at once

Work backwards from the read

• Decide the smallest number of conversions you need per variant before you read a result.
• Estimate the cost per conversion for this account from the last few weeks, and mark it as an estimate.
• Multiply the two to get the budget one variant needs for a fair read.

Turn budget into a count

• Divide the test budget by the budget one variant needs.
• Round down. A smaller number of variants with a fair read beats a larger number with none.
• If the answer is below two, nothing can be compared yet. Test one change against the control, or raise the budget.

When to launch more

• A broad first pass to find any strong idea can use more variants, as long as each one still gets its minimum budget.
• A test that must beat a strong control needs fewer, clearer differences, so each variant gets enough budget to be read.
• Do not add variants mid-test. A new variant starts its own read, and the old read is no longer clean.