How to measure Customer Acquisition Cost

The fully-loaded cost of acquiring one paying customer in a given period.

CAC = Total Sales & Marketing Spend ÷ New Customers Acquired

Why it matters: The denominator of unit economics. Get CAC wrong and every downstream metric — LTV:CAC, payback, Magic Number — is wrong.

3 tools that produce CAC

Side-by-side: how each tool produces this number, what to read before adopting, and where to find the official docs. Saasly does not integrate with these tools — this is a reference so you can pick the right one for your stack.

ToolCategoryHow it produces CACPricing
StripeBilling platformManual entryPay-as-you-go (2.
AppsFlyerAd attributionAutomaticFrom $0.
Saasly CalculatorManual calculatorManual entryFree forever, no signup.

Per-tool: what to know before you plug it in

Stripe

Manual entry

Billing platform

Subscription billing platform with built-in dashboards and SQL analytics (Sigma).

Before you adopt: Stripe has no view into ad spend, sales salaries, or CRM costs. You divide your own marketing/sales total by Stripe's new-customer count. Make sure the time windows match — ad spend in March should be paired with customers acquired in March, not signed-up later.
Pricing: Pay-as-you-go (2.9% + $0.30 per charge). Sigma analytics: free up to 1K charges/mo, then $0.02/charge.
Official docs for CAC Stripe home

AppsFlyer

Automatic

Ad attribution

Mobile measurement partner for ad attribution — connects ad spend to installs and subscriptions.

Before you adopt: Critical for mobile CAC — connects Meta / TikTok / Google ad spend to install → trial → paid conversion. iOS 14.5+ ATT impact: SKAN-based attribution is probabilistic, not deterministic. CAC for iOS is fuzzier than it was pre-2021.
Pricing: From $0.07 per non-organic install; enterprise pricing for higher volume.
Official docs for CAC AppsFlyer home

Saasly Calculator

Manual entry

Manual calculator

Manual-entry calculator that computes the core SaaS metrics with Skok-tier classification.

Before you adopt: Enter total sales & marketing spend and new customers acquired. The calculator returns CAC plus Skok-tier classification — pair with LTV to see your LTV:CAC ratio.
Pricing: Free forever, no signup.
Official docs for CAC Saasly Calculator home

Already have your numbers? Run the math.

The Saasly Calculator computes CAC (and 15 other SaaS metrics) from manual input — useful when you've pulled the underlying numbers out of one of the tools above and want a quick sanity check with industry benchmark percentiles.

Open the calculator

Other metrics

How to measure Customer Lifetime Value
The total gross profit a single customer is expected to generate over their entire relationship with you.
How to measure Monthly Recurring Revenue
The normalized monthly value of every active subscription, regardless of billing period.
How to measure Customer Churn Rate
The percentage of customers who cancel in a given period. Counts logos, not dollars.
How to measure Net Revenue Retention
How much revenue a cohort of existing customers generates compared to where they started — including expansion, contraction, and churn.
How to measure CAC Payback Period
The number of months of gross profit from a customer required to recover the cost of acquiring them.
How to measure SaaS Quick Ratio
The ratio of revenue gained (new + expansion) to revenue lost (churn + contraction) in a period.
How to measure Magic Number
Annualized net-new ARR generated for each dollar of the prior quarter's sales & marketing spend.
How to measure Gross Margin
The percentage of revenue left after the direct cost of delivering the service (hosting, support, payment fees, third-party APIs).
How to measure Trial-to-Paid Conversion
The percentage of users who start a trial and become paying customers.
How to measure Net Promoter Score
A survey-based score from the 0–10 'how likely are you to recommend us?' question, taking promoters (9–10) minus detractors (0–6).
How to measure DAU/MAU Ratio
The share of monthly active users who use the product on a given day — the standard 'stickiness' measure.