How to use the CAC calculator
The page has three tools, one for each question.
CAC gives the cost of winning one customer:
- Enter each type of sales and marketing spend for one period: ads, salaries (with commissions and payroll taxes), software, agencies and anything else. Use the same month or quarter for every line.
- Enter the new customers won in that period. Count new paying accounts only, not upgrades or customers returning after cancelling.
- Optionally add paid spend and paid customers from your attribution report to see paid CAC next to blended CAC.
CAC payback takes a CAC, the average monthly revenue per account (ARPA) and the gross margin, and returns the months needed to earn the CAC back. Add monthly churn to see how payback stretches once some customers cancel early.
Cost per lead converts campaign spend and leads into cost per lead, then uses your lead-to-customer conversion rate to show the CAC those leads imply. A target CAC gives the most you can afford to pay per lead.
How CAC, payback and cost per lead are calculated
Paid CAC = Paid channel spend ÷ Customers from paid channelsSpend and customers must cover the same period. Blended CAC is also called fully loaded CAC when it includes salaries and overhead.
Implied CAC = Cost per lead ÷ Lead-to-customer conversion rate
Highest affordable cost per lead = Target CAC × Conversion rate
A worked example
CAC. Company A, a fictional SaaS business, spent $45,000 on ads, $85,000 on sales and marketing salaries, $6,000 on tools and $14,000 on agencies in one quarter: $150,000 in all. It won 120 customers, so blended CAC is $1,250.00. Salaries make up 57% of the spend; leave them out and CAC would appear to be only $541.67.
Payback. A new account pays $150 a month at a 75% gross margin, which leaves $112.50 of gross profit. The $1,250 CAC is recovered after 11.1 months. With 2% of customers cancelling each month, the cohort as a whole breaks even after 12.4 months.
Cost per lead. A campaign spends $20,000 and produces 400 leads: $50.00 per lead. If 5% become customers, that is 20 customers and an implied CAC of $1,000.00, below the $1,250 target.
Blended CAC versus paid CAC
Blended CAC answers the question a CFO or investor asks: across everything we spend to grow, what does one customer cost? Paid CAC answers a narrower one: what does a customer from paid ads cost in media?
The two are easy to confuse. In the example, the $45,000 of paid spend produced 40 customers, a paid CAC of $1,125.00. Spread over all 120 customers, the same spend works out at only $375.00 each, because 67% of customers came from referrals, organic search and outbound. Using that lower figure as the cost of a paid customer understates it by a factor of 3.0, and scaling ad budgets on that basis usually disappoints: the extra customers bought with more ad spend cost the paid rate, not the blended one.
Both numbers depend on attribution. Last-click reports tend to credit paid search with customers who first heard of you elsewhere, so treat paid CAC as an estimate and look at the trend rather than one month.
How margin and churn change payback
Payback depends as much on gross margin as on CAC. With the same $1,250 CAC and $150 ARPA:
| Assumption | Payback | Churn-adjusted payback |
|---|---|---|
| 60% gross margin | 13.9 months | 16.1 months |
| 75% gross margin (the example) | 11.1 months | 12.4 months |
| 85% gross margin | 9.8 months | 10.8 months |
| 75% margin, ARPA $200 | 8.3 months | 9.0 months |
| 75% margin, 4% monthly churn | 11.1 months | 14.4 months |
A common rule of thumb in SaaS is a payback under 12 months, with up to 18 months often treated as acceptable. These are guidelines rather than standards: they vary by stage and segment, and enterprise businesses with annual contracts and low churn often run longer paybacks than self-serve products with monthly plans.
The churn column matters most for monthly plans. Simple payback assumes every customer stays until the CAC is repaid. At 4% monthly churn, a meaningful share of each cohort cancels before that point, and the survivors have to make up the difference.
What cost per lead tells you, and what it hides
Cost per lead is the earliest number a campaign produces, often weeks before anyone pays. On its own it says little, because a cheap lead that never converts costs more per customer than an expensive lead that usually does. Conversion is the multiplier:
| Lead-to-customer conversion | Implied CAC |
|---|---|
| 2.5% | $2,000.00 |
| 5% (the example) | $1,000.00 |
| 10% | $500.00 |
Halving conversion doubles CAC at the same cost per lead. That is why comparing channels on cost per lead alone can push budget toward sources that fill the pipeline but not the bank account. Use conversion rates measured over a long enough window for leads to close; in B2B sales that can be several months.
Common mistakes
- Mismatched timing. Spend this quarter often wins customers next quarter. If your sales cycle is long, compare spend with customers won one period later, or use a rolling average.
- Leaving out people costs. Salaries are usually the largest line. CAC built from ad spend alone is a media metric, not an acquisition cost.
- Counting upgrades and reactivations as new customers. They inflate the denominator and make CAC look lower than it is.
- Using revenue instead of gross profit for payback. This shortens payback by the gross margin ratio.
What this calculator does not include
- Expansion revenue. Payback assumes ARPA stays flat. Upgrades and price increases shorten it; the LTV:CAC calculator models expansion.
- Discounting. Payback counts future gross profit at face value.
- Attribution modeling. Paid CAC uses whatever customer count you enter; the calculator cannot correct for over-crediting.
- Onboarding and implementation costs that some companies treat as acquisition costs. Add them as “Other” if you do.
- Segment mix. One blended CAC can hide very different costs for small and large customers. Run each segment separately where you can.