Free tool
Paid Growth Budget Calculator
See what has to hold true for the next block of spend.
This paid growth budget calculator helps you pressure-test an advertising budget increase. It separates the current acquisition result from three additional spend bands, with a marginal customer acquisition cost assumption for each band.
The next customers may cost more or less to acquire than the customers already acquired. Enter that difference directly, then compare each band with the first-order and repeat contribution you expect within a stated horizon. The result shows conditional economics, without selecting an optimal budget or assuming your current CAC stays constant as spend grows. Use the Acquisition Profitability Calculator to check the customer economics that sit behind the budget scenario.
Three incremental spend bands · Entered marginal CAC · Stated contribution horizon
Current period
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Customer economics
Additional spend band 1
Additional spend band 2
Additional spend band 3
How this tool works
How the additional-spend scenarios work
For each band, divide its additional spend by its assumed marginal CAC to estimate new customers. First-order contribution before advertising is net revenue less product and other variable costs. Add expected repeat orders per acquired customer multiplied by repeat contribution per order, using the same horizon for all bands.
Multiply that before-ad customer contribution by the estimated customers in each band, then subtract the band’s spend. Bands are additional blocks, so the cumulative result adds them in sequence. Expected customer counts can be fractional because they are model outputs. Current average CAC is context, not an automatic input for the extra budget.
Estimated customers in a band = band spend ÷ marginal CAC. Band contribution after ads = estimated customers × before-ad contribution per customer − band spend.
A later spend band can weaken the combined result
Assume $100 first-order revenue, $35 product cost and $15 other variable costs. An average 0.5 repeat orders at $30 contribution adds $15, giving $65 before-ad contribution per acquired customer within the chosen horizon. A $5,000 band at $40 marginal CAC leaves $3,125 after ads. A further $7,500 at $55 leaves about $1,363.6. A further $10,000 at $75 loses about $1,333.3, taking combined additional contribution to about $3,155.3.
Your full calculation
| Measure | Result · USD |
|---|---|
| First-order contribution before acquisition | $50.0 |
| Repeat contribution per customer over 6 months | $15.0 |
| Contribution per customer before acquisition over 6 months | $65.0 |
| Current acquisition CAC | $40.0 |
| Modeled current contribution after spend | $6,250.0 |
| Band 1: additional spend | $5,000.0 |
| Band 1: modeled new customersExpected value; fractional customers are not actual observed people. | 125 |
| Band 1: contribution after spend | $3,125.0 |
| Through band 1: cumulative added contribution | $3,125.0 |
| Band 2: additional spend | $7,500.0 |
| Band 2: modeled new customersExpected value; fractional customers are not actual observed people. | 136.4 |
| Band 2: contribution after spend | $1,363.6 |
| Through band 2: cumulative added contribution | $4,488.6 |
| Band 3: additional spend | $10,000.0 |
| Band 3: modeled new customersExpected value; fractional customers are not actual observed people. | 133.3 |
| Band 3: contribution after spend | -$1,333.3 |
| Through band 3: cumulative added contribution | $3,155.3 |
| Total additional spend | $22,500.0 |
| Total modeled additional customers | 394.7 |
| Blended marginal CAC | $57.0 |
| Added contribution after spend over 6 months | $3,155.3 |
| Total modeled spend | $32,500.0 |
| Total modeled new customers | 644.7 |
| Combined modeled contribution over 6 months | $9,405.3 |
Questions & answers
Understanding your result
How do I calculate an advertising budget for growth?
Start with an explicit budget scenario and estimate the CAC of the customers added at that level. Compare the resulting first-order and horizon-limited repeat contribution with the extra spend. This tool helps test those inputs; it does not infer the best budget from current revenue.
Why does each spend band have its own CAC?
Marginal CAC describes the cost of customers added by that band, while current average CAC describes the customers already acquired. Audience reach, channel mix, creative and auction conditions may change as spend grows. Enter the assumptions you want to test rather than extending one average automatically.
How should I enter repeat orders per customer?
Use the average across all newly acquired customers within the stated horizon, including customers with no repeat order. Keep repeat contribution after its variable costs and before acquisition spend. Do not use repeats per repeat buyer as though every new customer will repeat.
Does positive modeled contribution mean I can afford the budget?
It means the entered contribution assumptions exceed the modeled acquisition spend. It does not establish the timing of cash receipts, stock funding, fixed costs or the likelihood of the assumptions. Check the cash commitment and operational capacity separately before increasing spend.