SEO vs PPC: compare cost per sale over 24 months
Ads cost the same per sale from day one. SEO costs more at first, then less once it ramps up. Enter your numbers to see when, or if, organic search becomes the cheaper channel.
24-month comparison
- PPC cost per sale
- $100.00
- SEO cost per sale, 24-month running
- $64.86
- SEO cost per sale at maturity
- $50.00
- SEO cheaper overall from
- Month 12
- SEO cheaper in a single month from
- Month 7
- Organic sales, 24 months
- 1,110
- SEO spend, 24 months
- $72,000
- Same sales bought with ads
- $111,000
- Revenue from organic sales
- $133,200
On these inputs, SEO's running cost per sale drops below paid search in month 12. After 24 months, buying the same sales with ads would cost $39,000 more than the SEO spend.
Each paid sale leaves $20.00 of order value after ad cost, before product costs.
| Month | Organic sales | SEO, that month | SEO, running | PPC |
|---|---|---|---|---|
| 3 | 15 | $200.00 | $300.00 | $100.00 |
| 6 | 30 | $100.00 | $171.43 | $100.00 |
| 9 | 45 | $66.67 | $120.00 | $100.00 |
| 12 | 60 | $50.00 | $92.31 | $100.00 |
| 15 | 60 | $50.00 | $78.95 | $100.00 |
| 18 | 60 | $50.00 | $72.00 | $100.00 |
| 21 | 60 | $50.00 | $67.74 | $100.00 |
| 24 | 60 | $50.00 | $64.86 | $100.00 |
How it works
The tool runs a simple month-by-month model for 24 months. Paid search is flat. SEO ramps up.
- PPC cost per sale
CPC ÷ paid conversion rate - Organic sales in month m (linear)
target sales × min(m ÷ ramp months, 1) - Organic sales in month m (compounding)
target sales × min(m ÷ ramp months, 1)² - SEO running cost per sale
SEO spend to date ÷ organic sales to date - Same sales bought with ads
organic sales over 24 months × PPC cost per sale
With the defaults, ads cost $100.00 per sale ($2.50 ÷ 2.5%). SEO costs $3,000 a month and reaches 60 sales a month after 12 months.
How to read the result
Look at the running cost per sale first. It counts the slow early months, so it is the honest figure for a budget meeting. The month it drops below the PPC line is your break-even point against ads.
The single-month figure tells you when SEO becomes the cheaper source of the next sale. That usually comes well before overall break-even. If neither happens within 24 months, SEO may still pay off later, but you should treat it as a long bet.
Assumptions and limits
- This is a model, not a forecast of your site. Every output depends on the target you type in.
- CPC and conversion rate stay flat. In real accounts they move with competition and seasons.
- SEO spend is the same each month. Organic sales do not fall when spend continues, and no ranking losses are modelled.
- It ignores product costs, so it compares acquisition cost only. Use the ROI calculator for profit.
- Organic and paid sales are treated as separate. In practice some searchers click both.
Common questions
Is SEO always cheaper than PPC?
No. SEO costs money before it brings sales, so it starts out far more expensive per sale. It only wins if organic sales reach a high enough level and stay there. This tool shows whether that happens on your numbers within 24 months.
Why is the running cost per sale different from the monthly one?
The monthly figure looks at one month alone. The running figure includes every dollar spent since month 1, including the early months with few sales. The running figure is the fairer one for a budget decision.
Should I stop paid search if SEO wins?
Not by default. Ads give fast, controllable volume and cover terms you do not rank for. Many teams use ads while SEO ramps up, then shift budget once organic sales prove out.
Where do I find a realistic organic sales target?
Start from keyword search volume, a likely click-through rate and your current conversion rate. Our guide on forecasting organic traffic walks through it step by step.
Want this on your real data?
We replace the guesses with your ad account, Search Console and GA4 figures. You get a channel plan with costs and a break-even month you can track.
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