What this calculator does
This calculator turns a sales target into an advertising budget. You tell it how many orders you want and what a customer currently costs you to acquire, and it returns the total spend required, the daily figure that spend implies, and the revenue and ROAS the plan would produce if the assumptions hold.
How to use it
- Enter the number of target sales you want in the period.
- Enter your cost per acquisition — what one completed purchase currently costs in ad spend, not cost per click.
- Set the campaign length in days so the calculator can work out a daily budget.
- Enter your average order value so the projection includes revenue and implied ROAS.
- Check the daily spend figure. If it is very small, the campaign will take a long time to gather enough data to optimise.
The formula, explained
The whole calculation rests on one assumption: that your cost per acquisition stays roughly where it is today. It rarely does. CPA usually rises as budget increases, because the cheapest, most responsive part of your audience gets reached first.
Treat the output as a floor rather than a forecast. A common working approach is to plan with today's CPA, then add fifteen to twenty percent headroom to the budget so a modest rise in acquisition cost does not stop the campaign short of the target.
A worked example
You want 300 sales over 30 days. Your current CPA is 12.50 and your average order value is 49.99.
Total budget is 300 × 12.50 = 3,750, which is 125 per day. Projected revenue is 300 × 49.99 = 14,997, giving an implied ROAS of exactly 4.0×. At 125 a day the campaign has enough volume to leave the learning phase quickly, which matters more than most beginners expect — budgets under about 20 a day generate data too slowly for the platform to optimise well.
| Target sales | 300 |
|---|---|
| Cost per acquisition | 12.50 |
| Total budget | 3,750.00 |
| Daily spend | 125.00 |
| Implied ROAS | 4.00× |
What a good result looks like
Daily spend, not total budget, determines how fast a campaign learns. These bands describe what to expect at different levels.
| Range | What it means |
|---|---|
| Above 100 per day | Fast learning and stable data. Decisions can be made within days. |
| 50 to 100 per day | Comfortable for a single product test on most platforms. |
| 20 to 50 per day | Workable but slow. Expect a week of noise before the numbers settle. |
| Under 20 per day | Very volatile. Results are hard to read and easy to misinterpret. |
Common mistakes
- Planning with a best-case CPA. Using the lowest CPA you have ever seen produces a budget that runs out before the target is hit. Plan with your recent average, not your record.
- Splitting a small budget across many campaigns. Five campaigns at 20 a day each learn far more slowly than one at 100. Concentrate spend until you have a winner.
- Stopping the moment ROAS dips. Daily ROAS is noisy. Judge against break-even ROAS over a full attribution window, not hour by hour.
- Forgetting creative production costs. Ad spend is not the whole marketing budget. Product samples, photography and editing all belong in the plan.
- Ignoring seasonality. Auction prices rise sharply in the fourth quarter. A budget built on September CPA will underdeliver badly in late November.
Frequently asked questions
How much should I spend on ads for dropshipping?
Enough to buy statistically meaningful data on each product you test. As a working rule, budget at least ten to twenty times your target CPA per product test — with a 12.50 CPA that means roughly 125 to 250 before you judge a product. Below that you are making decisions on noise rather than evidence.
What is a realistic daily ad budget when starting out?
Most new stores start between 20 and 50 per day per product. That is enough for the platform to gather data at a reasonable pace without risking a large sum on an unproven product. Once a product shows a CPA below your target, increasing budget gradually beats jumping.
Should I increase the budget on a winning campaign?
Yes, but gradually. Large sudden increases can push a campaign back into the learning phase and reset its performance. Raising daily budget by roughly twenty percent every couple of days is the conventional approach, watching CPA against your target as you go.
Does this calculator include organic sales?
No. It plans paid acquisition only. If some of your orders arrive through email, search or social organically, you will hit the sales target with less ad spend than the calculator suggests, which is a pleasant kind of wrong to be.
How do I know if my CPA assumption is right?
Divide total ad spend by the number of orders your own store recorded in the same period, rather than trusting the platform's attributed conversions. That blended figure is the honest one to plan with, and it is usually higher than the ad account shows.
How this fits with your other numbers
An ad budget is a hypothesis, not a commitment. The figure this calculator produces assumes your current acquisition cost holds as spend increases, which it usually does not. Treat the number as the minimum required to reach the target and keep a reserve for the point where the cheapest part of your audience is exhausted.
The daily figure matters as much as the total. Ad platforms need a certain volume of conversions before they optimise well, so a budget spread too thinly across too many campaigns produces noise rather than learning. Concentrate spend, find something that works, then widen — in that order, however tempting it is to hedge across several products at once.