Hey Sage · Free paid media budget planner · AUD
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Ecommerce paid media budget and channel mix planner
Build a channel mix from your unit economics and observed CPA range—not a universal 60/40 split. The planner can leave budget unallocated when the next dollar does not clear your target.
Allocate the next dollar, not a fixed percentage.
This planner first protects a small evidence budget for channels marked “Controlled test”. It then releases the remaining budget to scale-ready channels in small increments, choosing the lowest modelled marginal CPA that still clears the allowable CAC.
A channel stops receiving money at its monthly capacity, its allowable-CAC boundary or the total budget. Anything left stays visibly unallocated. That is often a more useful decision than forcing a neat pie chart.
Set the allowable CAC from contribution margin and the amount the business wants to retain.
Compare channel CPAs on one attribution basis and account for the normal conversion lag.
Scale only channels with measurement, assets, destination and operating capacity in place.
Fund a small, explicit learning budget without pretending a new channel is already scalable.
Add spend where the next modelled order is cheapest—not where last month’s average looks best.
Replace assumptions with observed marginal performance and update channel capacity monthly.
The arithmetic behind the mix.
Allowable customer acquisition cost
AOV × (contribution margin − desired post-ad contribution). At $140 AOV, 50% contribution margin and 10% retained after ads, allowable CAC is $56. The implied required ROAS is AOV ÷ allowable CAC, or 2.5×.
Channel curve
Each ready channel moves linearly from its starting CPA to its entered CPA at cap as budget is added. The planner allocates in roughly 200 increments, always choosing the lowest eligible next CPA. This is a transparent scenario model—not an auction forecast.
Sensitivity, not certainty
The conservative and stronger cases apply +20% and −20% to the modelled CPA. They show how exposed the plan is to cost changes; they are not confidence intervals or probabilities.
Official planning references
Validate the assumptions with Google Ads Performance Planner, Meta’s guidance on budgets and costs, Pinterest’s catalogue prerequisites and TikTok’s Smart+ web campaign guidance. Reviewed July 2026.
Paid media budget planning FAQ
How should an ecommerce brand split its paid media budget?
Start with allowable CAC and the marginal opportunity in each ready channel. Reserve controlled tests where learning is valuable, then release the balance where the next order is expected to clear the target. Avoid treating a generic platform percentage as strategy.
What is an allowable CAC for ecommerce?
Allowable CAC is the media cost per acquired customer that leaves the contribution your business requires. A simple starting formula is AOV multiplied by contribution margin before media, minus the share of revenue you want left after ads.
Should paid media budget be based on ROAS or contribution margin?
Use contribution margin to determine what the business can afford, then translate the resulting allowable CAC into a required ROAS for channel planning. Platform ROAS without margin context can reward revenue that does not create enough contribution.
How much budget should go to Google Ads versus Meta Ads?
There is no durable universal ratio. Google and Meta capture and create demand differently, so compare their incremental or marginal economics, available demand, creative readiness and monthly capacity on a consistent attribution basis.
How much should I spend testing a new ad channel?
Fund enough target outcomes to learn something useful while keeping the downside controlled. This planner uses starting CPA multiplied by your chosen test-order count, capped by the channel’s monthly capacity and the total budget.
Why would a media plan leave budget unallocated?
Because the next estimated dollar may exceed allowable CAC, all ready channels may have reached capacity, or channels may be deliberately on hold. Unallocated budget can protect margin until better demand, creative or evidence appears.
What is the difference between average CPA and marginal CPA?
Average CPA describes all spend divided by all attributed acquisitions. Marginal CPA estimates the cost of the next acquisition as spend rises. Budget decisions should pay close attention to marginal cost because averages can hide declining efficiency at the edge.
How often should I reallocate paid media budget?
Reforecast monthly and use shorter release checkpoints when spend or performance changes quickly. Wait for normal conversion lag, major promotion effects and data quality issues before moving budget from noisy daily results.
Want a channel plan tied to the real P&L?
Hey Sage can reconcile channel evidence, creative capacity, demand and margin into a release plan your team can govern.
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