How to Calculate a Google Ads Budget for Shopping

A Google Ads budget is the average amount a campaign may spend per day. Google turns it into a monthly limit with one multiplier, 30.4, and lets a single day run to twice the setting.

That conversion is the easy half. The half that decides profit is what an order may cost: in my worked example, an €80 order at a 30% margin breaks even at €24.

Every figure is calculated from Google’s published spending rules and one illustrative shop, so you can redo each sum with your own numbers.

How do you convert a monthly budget to a daily budget?

Divide the monthly budget by 30.4 to get the average daily budget, and multiply a daily budget by 30.4 to get the monthly limit.

Google’s budget and spending-limit guidance uses 30.4 because it is the average number of days in a month (365 ÷ 12).

Daily amounts are rounded to the cent, so 30.4 times the rounded figure can miss the target by a few cents.

The Google Ads budget calculator does the same conversion and also shows how many clicks the daily budget buys per product.

Why does Google spend more than the daily budget on some days?

Google spends up to twice the average daily budget on a single day, because it predicts more clicks and conversions on some days than others. Its own example is a $10 average daily budget with a $20 daily spending limit.

Average daily or campaign total budget: which should you use?

Use an average daily budget for always-on Shopping and Performance Max campaigns, and a campaign total budget for a promotion with a fixed start and end date.

Google’s campaign budget documentation describes both: a $50 daily budget caps a month at $1,520, while a total budget caps the whole campaign period.

With a campaign total budget, Google paces delivery over the remaining days and never charges more than the total. It only works with some bidding strategies, so check the campaign first.

A campaign’s average pace is not its required pace. When you improve Google Ads budget pacing, separate a real overspend from spend Google concentrated on stronger days.

Neither type buys profitable orders by itself. The budget sets the ceiling; the economics below decide whether it should be reached.

How to calculate a Google Ads budget from your margins

Start from what one order contributes before advertising, then work back to the clicks you can afford. The example shop has an €80 average order excluding VAT and a 30% contribution margin after product and variable order costs.

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What an €80 order at a 30% margin can pay for its clicks

Cost per order	Cost per order
Break-even (all contribution)	€24
Ceiling (keeps €6 per order)	€18
Forecast at €0.60 and 5%	€12

The €0.60 is the shop’s own Shopping figure, and it should stay that way in your sum.

For context, Addy0’s small-business Google Ads guide quotes an average Search CPC of $5.26 across 16,446 US campaigns from April 2024 to March 2025. That is a Search benchmark, not a Shopping one.

At €12 per order, the example’s ROAS is 6.67 (€80 ÷ €12). In profit on ad spend (POAS) terms that is 6.67 × 0.30 = 2.0: every euro of advertising returns €2 of contribution, against a break-even POAS of 1.0.

Check your own floor with the break-even ROAS calculator before you set a target ROAS. A revenue target alone hides the costs that decide whether an order makes money.

Does a €3,000 budget break even?

A €3,000 budget breaks even only when cost per click ÷ conversion rate stays at or below the €24 an order contributes. The same budget gives very different results at different click prices and conversion rates.

These are arithmetic scenarios, not benchmarks. “Keeps” means contribution after advertising, before overhead.

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Cost per order at three click prices, against €24 of contribution

Average cost per click	2% conversion rate	5% conversion rate
€0.60 per click	€30	€12
€1.20 per click	€60	€24
€2.00 per click	€100	€40

Cheap clicks are not enough on their own. At €0.60 a click, a drop from 5% to 2% conversion turns €12 kept into €6 lost.

What conversion rate do your clicks need?

The required conversion rate is cost per click ÷ maximum cost per order. A €1.20 click against the €24 break-even needs 5%; against the €18 operating ceiling it needs 6.7%.

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The conversion rate each click price needs

Average cost per click	To break even (€24 per order)	To keep €6 per order (€18 ceiling)
€0.60	2.5%	3.3%
€1.20	5.0%	6.7%
€2.00	8.3%	11.1%

If your products can’t sustain that rate, the click price is too high for your margins. The Google Ads metrics calculator works out CPC, conversion rate and CPA from your campaign report.

What to do when the sum fails

Don’t increase the budget to get more orders when each order loses money: it buys more of the same loss. Change one of the inputs instead.

A smaller budget only gets more efficient when it changes which auctions or products get the money.

How should you split the budget across products?

Split the budget by contribution per click, not by revenue. Give the money first to products with profitable demand and stock, and add more only while the extra orders still pay for their clicks.

Product Metrics segments every product into six segments by its advertising clicks and its return against the product’s own target, and sends each segment to Merchant Center as a label.

These shares are a hypothetical starting point, not observed benchmarks; budget you don’t need can stay unspent.

“Below goal” never means below break-even. It gives Stars room to win more auctions while each order still pays for itself.

Product Segmentation for Google Shopping shows the six segments and the campaign structure they feed.

Google’s budgeting guidance sets a budget per campaign, or one shared budget for several. Performance Max spreads that single budget across Search, YouTube, Display, Discover, Gmail and Maps.

So a healthy campaign average can hide products that lose money on every click. Finding them by hand means checking clicks, return, margin and stock for every product, every week.

A Star without enough stock can’t absorb the share its history suggests. A Drainer often has a price or feed problem rather than a demand problem.

When should you increase your Google Ads budget?

Increase the budget only when three things hold: the campaign spends its full allowance, the cost per order on completed purchases stays under your ceiling, and Google Ads purchases match your shop’s orders.

Google’s Performance Max guidance stresses accurate conversion tracking and conversion values, because automated bidding works on the values you send, not on your margins.

Google Ads conversions and shop orders never match exactly: attribution differs and purchases arrive after the click. Investigate a gap you can’t explain.

Missing high-value orders make profitable products look weak, and duplicates make weak ones look profitable. Purchases lost to ad blockers are one cause; you can test ad-blocker conversion tracking in your own browser.

Treat an undercount as a sensitivity test, not proof that losing campaigns are secretly profitable. Adjust only for purchases you can confirm are missing, never by one blanket percentage.

Judge each increase on the extra contribution it brings over complete conversion cycles. The next euro rarely performs like the historical average.

Final thoughts

The daily number is just the monthly figure divided by 30.4. The real budget decision is the cost per order your margin allows, and that differs per product.

Run your own order value, margin, CPC and conversion rate through the Google Ads budget calculator, then check what the spend leaves after product and order costs with the POAS calculator.

If you want a second check on the monthly-to-daily split, Assertive Agency’s budgeting tool for Google Ads campaigns runs the same conversion. Keep the monthly amount next to the daily setting.

If someone asks what other advertisers spend, Silva Marketing’s overview lets you compare 2026 Google Ads budgets. Another shop’s allowance says nothing about what your orders can afford, so use it to challenge assumptions, not to set your number.