What ROAS do you actually need?
Break-even ROAS from your real margins — not just revenue divided by spend.
Example numbers — edit anything and they're yours.
Your margins — unlocks break-even 4 inputs
% of ex-GST order value
+ per order
Enter your numbers
ROAS appears instantly; add margins and the dial learns where your break-even actually sits.
Show the working →
Profit sensitivity — ROAS × monthly spend
Monthly profit after ad spend at your margins · green above break-even, red below
| Enter margins above to build the grid |
Target mode
A ROAS without a break-even line is a vanity metric.
ROAS — return on ad spend — is attributed revenue divided by ad spend, and on its own it tells you almost nothing. Whether 3.0× is excellent or a slow leak depends entirely on what you keep from each order after product costs, shipping, payment fees and GST. This calculator computes that break-even line from your real unit economics, marks it on the dial, and shows profit — per order, per month, and across a whole grid of spend and ROAS scenarios. Built by a studio that runs a 30,000-SKU store and does this maths for real.
ROAS, break-even, MER — in plain English.
ROAS
Return on ad spend
Attributed revenue ÷ ad spend. Spend $1,000, get $3,000 attributed, ROAS is 3.0×. It measures revenue efficiency per ad dollar — not profit, and only within what the platform can attribute.
BREAK-EVEN ROAS
The line that matters
Reported order value ÷ contribution margin per order. Keep $35 of a reported $100 order and your break-even is 2.86× — below that, every "successful" order loses money. It's your margin structure expressed as a ROAS.
MER
Marketing efficiency ratio
Total revenue ÷ total marketing spend, across all channels, no attribution needed. The sanity check on platform-reported ROAS: when MER and ROAS diverge hard, your attribution — not your marketing — usually moved.
Straight answers.
What is a good ROAS?
There isn't a universal one — it's entirely a function of your margins. A store keeping 50% of each order breaks even at 2.0×; a store keeping 25% needs 4.0× just to stand still. Compute your break-even with the tool above, then judge campaigns against your line, not an industry average.
How do I calculate break-even ROAS?
Break-even ROAS = reported average order value ÷ contribution margin per order. Contribution margin = order value ex GST − COGS − shipping − payment fees − other per-order costs. The "Show the working" panel above renders this with your own numbers substituted in.
What's the GST trap for Australian stores?
Ad platforms report revenue including GST, but one eleventh of every inclusive dollar is the ATO's, not yours. If you compute margins on inclusive revenue, your break-even ROAS looks roughly 10% healthier than reality — which is exactly enough to make a losing campaign look like a winner. The GST toggle above strips it correctly (÷ 11).
ROAS vs MER — which should I use?
Both. ROAS steers individual campaigns; MER (total revenue ÷ total marketing spend) sanity-checks the whole system without trusting attribution. If ROAS looks great while MER slides, the platforms are probably taking credit for orders they didn't drive — or your tracking is broken.
Why might my reported ROAS be wrong?
Because ROAS inherits every flaw in your conversion tracking. Since the August 2026 Shopify checkout upgrade removed legacy checkout scripts, many stores' Meta and GA4 purchase counts stopped matching their real orders. Run the free Tracking Health Check — if purchases are going missing, fix that before optimising to the number.