Limited by budget: when to increase and when not to

The status describes a gap and recommends nothing

The “Limited by budget” status measures your budget against the available volume, not against your profit. According to Google, the average daily budget is lower than the recommended amount to capture all available impressions and clicks for your current settings. Google then reduces how often your ads appear so that the budget is not used up too quickly, and states itself that a campaign with this status can still be successful.

For you as a retailer, this is a description: there would be more to buy. What it leaves open is whether the extra pays off, and that depends solely on the return from the additional clicks. The campaign's average ROAS does not answer that, because it contains all the good clicks you already get anyway.

Marginal return against break-even ROAS

The decision needs two figures that never appear side by side in the account:

• Marginal ROAS = (new conversion value minus old conversion value) divided by (new cost minus old cost)
• Break-even ROAS = 1 divided by the contribution margin rate before ad spend

If the marginal ROAS is above the break-even ROAS, you earn money on the next budget step. If it is below, you lose money, even if the average still looks good.

A worked example with invented, round figures: suppose a shop has a 25% contribution margin before ad spend, which means a break-even ROAS of 4. It increases the monthly budget by 20%.

Case B is the expensive one. The ROAS of 4.67 sits clearly above break-even in the report, and yet the increase has cost €1,500 a month. If you only check whether the campaign is still hitting its target, you will not see that. The calculation assumes that the conversion value matches the basis of the margin rate, meaning the same treatment of tax and returns. If you already report margin as the value, the break-even ROAS is 1.

What lost share tells you and what it does not

Lost impression share shows how much volume the budget cuts off; it says nothing about what that volume is worth. According to Google, Search lost IS (budget) is the percentage of time that your ads weren't shown on the Search Network due to insufficient budget, available at campaign level only. Behind it is an estimate of the possible impressions.

I would therefore use the figure as a pre-filter, not as an argument. There is no fixed threshold above which you have to increase. Three readings still help, in my assessment:

• 30% lost share does not mean 30% of revenue left on the table. You learn that auctions are missing, not how well they would have converted.
• If the share lost to ad rank (Search lost IS, rank) is clearly larger than the share lost to budget, money is probably the weaker lever. The campaign is then losing mainly in the auction.
• If the budget figure rises without you changing anything, the campaign has not necessarily got worse. According to Adalysis, this is usually due to a change in search volume, typically seasonality, and rising CPCs push it up too, because the budget is used up faster. With higher CPCs, more budget would mean more money for the same clicks.

Estimating marginal ROAS when the simulator fails

The obvious tool is often missing exactly here. The simulators may not be able to provide estimates if the campaign has reached or nearly reached its average daily budget at least once in the last 7 days, and with shared budgets the campaign simulator is not available at all. Two ways out remain.

Performance Planner. The agency Precis describes the method: read off cost and conversion value for the next point above and below current spend and divide the differences. According to Precis, the result is a guide figure based on historical data. For the question of whether you are clearly above or clearly below break-even, that is usually enough. I would not decide close calls with it.

A small step with measurement. Google advises waiting 1 to 2 conversion cycles after an increase before you evaluate performance. There is no Google guideline for the size of the step: PPC specialist Nils Rooijmans rarely increases by more than 20% a week, which I consider workable. With a long conversion lag, the waiting time sets the pace. Afterwards, you calculate the difference from the previous period. Seasonality and promotions run alongside, so I would compare the figure with campaigns that had no change, and change nothing else in the budget step, not even the target.

“Lowering the target” means opposite things for CPA and ROAS

Lowering a target CPA makes the campaign stricter, lowering a target ROAS makes it looser. With a tight budget, that is the difference between better and worse returns for the same money, because as long as the budget remains the limit, spend is fixed. The lever is then the price per result.

Since 17 August 2026, this carries more weight (Google Help as of November 2026). According to Google, budget-limited campaigns with a target CPA or target ROAS now deliver closer to the target that has been set. Google's example: with a target CPA of USD 10 and an actual CPA of USD 5, the campaign moves towards USD 10 without intervention; if you want to keep the USD 5, enter it as the target and increase the budget later. Details are in the article on budget-limited campaigns with target ROAS.

Applied to the shop from the worked example, simplified to a €1,000 daily budget that is spent in full: with a target ROAS of 4 and an actual ROAS of 6, conversion value falls from €6,000 towards €4,000. Contribution margin after ad spend drops from €500 to zero, with spend unchanged. A target that is too loose in a budget-limited campaign costs money without anyone having touched anything.

These mechanics determine which lever fits when. The table is my assessment:

Google flags the fourth case as a separate status: bid limits or targets are holding the campaign back, for example a target CPA that is too low or a target ROAS that is too high. More budget changes little there. How far to move a target in one go is a separate question: changing target ROAS.

Google itself recommends a budget buffer plus a target that reflects your desired efficiency. That only fits the table under one condition: the target has to be high enough that you want even the last click it buys. A target ROAS exactly at break-even means zero contribution margin on average, and the buffer would then have nothing to earn.

Brand objectives calculate differently

The comparison with break-even assumes that the campaign is meant to make money today. With brand or range objectives, you deliberately put return second, so a marginal ROAS below break-even is not a mistake, as long as you know the price and cap it. The trade-off is covered in the article on deliberately advertising below break-even.

With few conversions, the estimate does not hold up. If a few orders more or less shift the marginal ROAS from 3 to 6, the figure is no basis for a decision. In that case I would set the budget according to the contribution margin you are willing to risk, and only do the calculation once there is enough data.