When the euro falls, your break-even ROAS rises
If your goods are invoiced in dollars and you sell in euros, a weaker euro raises the cost of each order and, with it, the ROAS you need to break even. The thinner your margin, the more a small currency move costs you. Recompute the line, then set your target against it.
By Joris van Huët, Founder & CEOPublished 5 min read
Run the numbers for your store: the free break-even ROAS calculator, or the free contribution margin calculator.
Yes, if any of your costs are priced in dollars. A weaker euro raises what each order costs you in euros, which leaves less of the price to pay for ads, so the ROAS you need to break even goes up, and the thinner your margin, the more it goes up.
The dollar gained nearly 2.2% against the euro in September 2026, and a euro bought about 1.135 dollars at the time of the report (Reuters, published 29 September 2026, updated 30 September 2026). That is a headline for a treasurer. For a brand it is a change to a line in the ad account.
Does a weaker euro change my break-even ROAS?
It does, through your margin. Break-even ROAS is the price divided by what is left of it after every cost that scales with an order:
break-even ROAS = price / (price - cost per order)
That is the same as one divided by your contribution margin. When the cost per order rises, the margin shrinks and the divisor falls. Assume the whole cost is priced in dollars and the dollar gains 2.2%. This is what it does at four margins:
| Cost as a share of price | Break-even ROAS now | After a 2.2% rise in cost | Change |
|---|---|---|---|
| 40% | 1.67 | 1.69 | +1.5% |
| 50% | 2.00 | 2.04 | +2.2% |
| 60% | 2.50 | 2.59 | +3.4% |
| 70% | 3.33 | 3.51 | +5.4% |
The table is arithmetic, not a benchmark, so use your own margin. Its shape is the point: the same 2.2% move costs a 30% margin more than three times what it costs a 60% margin, and the brands with the least room feel it first.
Which of your costs actually move?
Only the ones priced in dollars:
- Goods your supplier invoices in dollars. The landed cost rises once the next order is placed at the new rate.
- Freight quoted in dollars.
- Not the costs you pay in euros. Fees on European payment methods, local pick and pack, and shipping inside the euro area stay where they were. Scale the move by the dollar share of your cost, not the whole of it.
The move helps if you sell to customers in the US in dollars while your costs are in euros: each dollar of revenue is worth more euros, and break-even ROAS falls. Most brands that buy in dollars sell in euros, so the first case is the common one.
Why does the new line arrive late?
Three lags keep the change out of your account until it hurts:
- Stock bought earlier carries the old rate. The new rate reaches your cost of goods with the next order, so the margin drops in steps, not on the day the euro moves.
- Prices on the shelf change more slowly than costs. A price rise needs a decision, a test and a launch.
- ROAS targets change slowest of all. The number in the ad account was set at a planning meeting, against a margin that has since moved. Your landed cost went up and your ROAS target didn't covers the same lag for tariffs and freight.
What should you hold the new line against?
The ROAS your ads caused, not the one they were credited with. Each platform counts purchases inside its own window, so together they can claim more sales than the store took. The ad platform over-reporting checker shows by how much, and the break-even ROAS calculator and the contribution margin calculator redo the sum at today's rate.
This week:
- Split your cost per order into dollar-priced and euro-priced parts.
- Recompute contribution margin at today's rate and divide one by it.
- Put the new break-even, plus the buffer you need, into the ad accounts.
- Compare it with the ROAS your ads caused, not the platform's.
Where a read fits
Later, once you sell through two or more channels and have a few months of GA4 history, a causal attribution read like Causality Engine's can show which channels clear the new line on what they caused, not on what they were credited with. It reads the GA4 Attribution paths export and shows what each channel caused next to what last-click gave it, with Direct split back to the channels that sent those buyers. Every channel gets a data-health score from 0 to 100 and a next step. It takes 1 to 2 minutes and costs EUR 99 once per upload, excluding VAT, with a full refund within 30 days, no questions asked. The first finding is free: your browser works out how many days buyers who saw two or more channels take to convert, and the file never leaves your machine.
Sources, accessed 30 September 2026: Reuters, via Investing.com (published 29 September 2026, updated 30 September 2026). The margin table is arithmetic on an assumed cost that is wholly priced in dollars.
Related answers
- Your landed cost went up. Your ROAS target didn't.
- The 2.5x markup rule and your break-even ROAS
- Black Friday discount depth: the loss you book in advance
- Blended MER vs platform ROAS: which should drive spend?
- Why your Meta ROAS and Shopify revenue never match
- First order at a loss? Judge it on payback, not ROAS
Frequently asked questions
Does a weaker euro change my break-even ROAS?
Yes, when part of your cost is priced in dollars. That part costs more in euros, your margin per order shrinks, and break-even ROAS, one divided by that margin, rises. A 2.2% rise in cost moves it by about 1.5% at a 60% margin and by about 5.4% at a 30% margin.How do I calculate break-even ROAS?
Divide the price by what is left after every cost that scales with an order: break-even ROAS = price / (price - cost per order). It is the same as one divided by your contribution margin.Does a weaker euro help if I sell in the US?
It can. Revenue in dollars is worth more euros, so if your costs are in euros your margin per order rises and break-even ROAS falls. Any costs you pay in dollars cancel part of that.How often should I update my ROAS targets?
Whenever a cost that scales with an order moves: a currency, a freight rate, a supplier, a fee. Put it on the same calendar as your supplier review, not the annual plan.
Go deeper: Causal attribution, explained.
Sixty-second versions of these ideas: Causality Engine on YouTube Shorts.
Keep reading
Terms in this article
- AttributionAttribution identifies user actions that contribute to a desired outcome and assigns value to each. It reveals which marketing touchpoints drive conversions.
- Black FridayBlack Friday is the day after Thanksgiving in the United States. It marks the start of the Christmas shopping season and is a major sales event for retailers.
- Causal AttributionCausal Attribution uses causal inference to determine which marketing touchpoints genuinely cause conversions, not just correlate with them.
- CausalityCausality is the relationship where one event directly causes another, essential for identifying specific actions that drive desired outcomes in marketing.
- ClickClick is the action a user takes to interact with a digital advertisement, redirecting them to a website or landing page. Clicks are a fundamental metric for measuring ad engagement and a primary input for click-based attribution models.
- RevenueRevenue is the total income generated by the sale of goods or services related to a company's primary operations.
- ShopifyShopify is an ecommerce platform for creating online stores and selling products. Attribution modeling shows which marketing channels drive traffic and conversions within Shopify.