A Shopify store should keep spending on ads until a new customer costs more than the contribution their first order leaves after product, shipping, payment fees and returns, plus any repeat orders you can rely on. That ceiling comes from your margin, not a percentage rule, and it moves month to month.

What do Shopify advertising costs actually include?

Media is the largest line in Shopify advertising costs, not the only one. Most Shopify brands buy Meta and Google first and TikTok next, and each platform bills for impressions or clicks whether or not anyone buys. Shopify now sells its own option too. Its help center describes Shop Campaigns as ads placed in the Shop app, on shop.com, through the Shopify Product Network and on some outside sites, where you set an average acquisition cost and pay only when a customer converts. That sounds safer than an auction, and sometimes it is. The same help pages note that orders within seven days of a paid click are credited to the campaign, and that returning customers can appear even in a campaign aimed at new ones. Around the media sit the costs people forget: management fees, creative production, and the apps for attribution, email and reviews. Add all of them before you divide by new customers, or your acquisition cost will look healthier than it is.

How do you work out an ad budget from margin?

Start with contribution per order: revenue minus product cost, shipping, payment fees and the returns you expect. Take a simple example. An $80 average first order at a 50% contribution margin leaves $40. If the first order has to pay for itself, $40 is the most you can spend to win that customer, which equals a break-even ROAS of 2.0 on new-customer revenue. If your Shopify data shows customers reliably add another $20 of contribution within a year, and you have the cash to wait for it, the ceiling rises to $60. The budget then follows from volume: multiply the ceiling by the number of new customers you can buy below it, and stop adding spend once the next customer costs more than the ceiling. Take the inputs from Shopify's own reports, including its split of first-time and returning customers, rather than from what the ad platforms claim.

Why do percentage rules of thumb mislead?

Percentage rules borrow numbers from businesses that look nothing like yours. In Gartner's 2026 CMO Spend Survey, total marketing budgets averaged 7.8% of company revenue, but most respondents ran companies with more than $1 billion in revenue, and that figure covers all marketing, not paid acquisition alone. An online brand that wins most of its customers through ads will usually spend a larger share, and whether that is healthy depends on margin and repeat rate rather than the share itself. A brand with high gross margin and strong reorders can afford far more per customer than one with thin margins and heavy returns. Fixed percentages also ignore price. Meta's results for the second quarter of 2026 showed the average price of an ad up 12% on a year earlier, so the same slice of revenue now buys less reach. Every account review at plaidtesting.com/paid-media-audit starts by rebuilding this ceiling, because every later budget call depends on it.

How should the budget change from month to month?

Review it monthly against two numbers: ad spend as a share of sales, and new-customer cost against the ceiling you set. Platform benchmarks help only as context. Triple Whale's Meta benchmarks for August 2025 to July 2026, drawn from more than 40,000 brands, put the median CPA at $38.99 and the median CPM at $15.06, about 13% higher than the prior year, but a median knows nothing about your margin. If new-customer cost sits well under the ceiling and the next slice of spend still brings customers at that cost, raise the budget. If the share of sales climbs while new-customer counts stall, the extra money is mostly buying back customers you already had. Expect the ceiling itself to shift with promotions, seasonality and stock. If you are deciding who should make these calls, here is what a Shopify marketing agency should own, and what is better kept with your team.

An athletic apparel brand I work with spent $457.4K on ads across every channel in June 2026 against $1.73M of sales, about 26% of sales. A year earlier the figure was about 31%, $421.1K on $1.36M. That is a store-level blend: it does not show which channel did the work, no holdout test measured what the ads alone caused, and new products and pricing helped sales grow as well. The lesson is to judge the budget as a share of sales and contribution, month by month, rather than holding it to a fixed rule.

Before you set next month's budget, write down your contribution per order and the most you will pay for a new customer, then let spend follow those two numbers.