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Roughly 15% per step on a Smart Bidding campaign, gated on cost per acquisition at each rung, with no pre-set endpoint. Step up while the cost holds and stop the moment it degrades.
On this page
- Why increase budgets in steps rather than jumps?
- What should gate each budget increase?
- When can I change a budget faster than 15%?
- When can I read the result of a budget change?
Why increase budgets in steps rather than jumps?
A large increase pushes real incremental spend into less efficient inventory faster than the algorithm can re-find efficient placements. Cost per acquisition spikes and you cannot tell whether you found a genuine ceiling or simply outran the bidder.
The failure is not the size of the number. It is that a jump destroys your ability to read the result.
What should gate each budget increase?
The step size matters less than gating each rung on the outcome. Raise, wait for a settled read, check cost per acquisition, then decide. Weekly-ish cadence on most accounts.
Do not stack changes inside a gate window. Change the budget and the target in the same week and you have no read on either.
When can I change a budget faster than 15%?
| Situation | Move |
|---|---|
| Killing a zero-conversion campaign | One move. Nothing to disrupt. |
| Cutting an unused ceiling | One move. If it is not spending to cap, lowering the cap has no delivery impact. |
| Dropping a target ROAS floor | Bounded by the budget cap, so it cannot run away. Different risk class. |
| Un-strangling a dead campaign | One decisive move. Staircasing keeps it dead for months. |
That last one is the exception people get wrong most often. The 15% rule is for scaling something that works. A campaign that has been strangled to near-zero is not working, and stepping it up slowly means each increment is swamped by the pool it is measured against.
When can I read the result of a budget change?
A budget change read on unsettled data is not a read. Conversion-date figures take about 4 days to finish being written — measured against a saved snapshot on an apparel account, windows ending 4+ days ago backfilled 0.0%, a window ending 1 day ago backfilled +83.7%.
Raise on Monday, read the following Monday, and only count days that are at least 4 days old.
Related questions
How do I stop Performance Max from spending my budget on YouTube?
You cannot switch YouTube off inside a Performance Max campaign. What you can do is see exactly how much it is costing you, fix the signal that is sending it there, and decide whether to split the campaign. Read the full answer.
How do I find out how much of my Performance Max spend is going to my own brand searches?
Performance Max does not report brand spend as a line item, so you build it from the search terms it does expose plus the network split — and accept that the figure is a floor, not a total. Read the full answer.
Why does my Google Ads ROAS swing so much from week to week?
Before assuming the account is unstable, check whether the measuring instrument changed underneath the series. Every published answer says "wait for more data" or "widen the window." None raise the possibility that the ruler moved. Read the full answer.
Written by Usama Khan, who runs Google Ads for e-commerce brands and home-services companies at AdventurAds. Figures are from accounts under active management and are anonymised. Last reviewed 2026-08-26.
