CPA, cost per lead and cost per customer, defined

CPA (cost per acquisition) measures what you pay in advertising to get one conversion. In Google Ads, the Cost / conv. column calculates it by dividing total cost by the number of conversions. So everything depends on what you count as a conversion:

  • Cost per lead (CPL) = ad spend ÷ number of leads. A lead is an inquiry: a form fill, a call, a quote request. It is the metric that matters for service businesses, which close the sale offline.
  • CPA = ad spend ÷ number of sales or signed customers. In ecommerce, it usually means cost per order.
  • Cost per customer = cost per lead ÷ close rate. It is the real CPA of a business that sells on quotes.
  • Maximum CPA = average sale value × gross margin. Above it, the first sale costs more in ads than it brings in gross profit.
  • Lifetime maximum CPA = customer lifetime value (LTV) × gross margin, for businesses whose customers come back.

Our glossary covers each one: CPA, customer acquisition cost and customer lifetime value.

How to use the calculator

  1. Pull ad spend (the Cost column in Google Ads) and the number of leads for the same period, excluding sales tax.
  2. Count the customers you actually signed from those leads, in your CRM or quote tracker.
  3. On the CPA & cost per lead tab, read your cost per lead, actual CPA and close rate.
  4. Open the Max CPA tab: enter your average sale value and gross margin, then your customer lifetime value if customers come back.
  5. Finish on the Cost per customer tab to see how much you can afford to pay for a lead.

Worked examples

A home services company spends $1,500 a month on Google Ads, gets 60 inquiries and signs 12 jobs. A job brings in $800 on average, at a 40% gross margin. These are the calculator's default values.

  • Cost per lead: $1,500 ÷ 60 = $25.
  • Actual CPA: $1,500 ÷ 12 = $125, with a close rate of 12 ÷ 60 = 20%.
  • Maximum CPA on the first sale: $800 × 40% = $320. At $125, every customer is profitable from the first job.
  • Maximum cost per lead: $320 × 20% = $64. As long as a lead costs less than $64, the campaign pays.
  • If a customer spends $3,000 over the whole relationship, they leave $3,000 × 40% = $1,200 in gross profit. A 3:1 LTV:CAC ratio would put the target CPA around $400.

Second case, an online store: $2,000 in ad spend for 80 orders, a CPA of $25. With a $60 average order value and a 30% gross margin, the maximum CPA is $18. The store loses $7 on every first order: it only makes money if customers order again.

What is a good CPA?

No CPA is good in absolute terms. $125 is an excellent CPA for a job that leaves $320 in gross profit, and a disaster for a $60 order. A good CPA stays below your maximum CPA, with enough volume to grow total profit.

Pushing CPA down at all costs often shrinks the number of customers. With $320 of gross profit per customer, a $150 CPA on 20 customers earns 20 × $170 = $3,400, while a $90 CPA on 5 customers earns only 5 × $230 = $1,150.

For market context, LocaliQ and WordStream's 2026 search advertising benchmarks put the average cost per lead at $66.69 across industries, with an average conversion rate of 8.18%. The spread is wide: from $26.84 in Arts & Entertainment to $131.63 for Attorneys & Legal Services. Use those figures to sanity check your numbers, not to replace your own ceiling.

CPA vs. CAC vs. ROAS

CPA only counts the ad spend of a campaign. Customer acquisition cost (CAC) adds up everything it took to win the customer: ads, agency fees, tools, sales time. So CAC is always equal to or higher than CPA, and it is the number to compare with customer lifetime value.

ROAS looks at revenue instead of customers. A $320 maximum CPA on an $800 sale is the same threshold as a break-even ROAS of $800 ÷ $320 = 2.5, which is exactly 1 ÷ a 40% margin. Both lead to the same ceiling: one per customer, the other per dollar spent.

How to set target CPA in Google Ads

Target CPA is an automated bid strategy that sets bids to get as many conversions as possible at the average cost per conversion you choose. Google's help center sets three ground rules:

  • Requirement: conversion tracking must be set up before you create the strategy.
  • Starting point: the recommended target CPA is your average CPA from the last 30 days, adjusted for conversion delays.
  • Evaluation: Google recommends measuring performance over periods that include at least 30 conversions.

Our method: start from your actual CPA over the last 30 days, check that it sits below the maximum CPA calculated above, then adjust in steps. If your conversions are leads, compare the target with your maximum cost per lead, not your cost per customer. To bid on value instead, use the ROAS calculator.

Common mistakes

  • Comparing cost per lead with the gross profit of a sale: a lead is not a customer yet.
  • Counting phone number clicks or contact page visits as conversions, which inflates lead counts.
  • Mixing tax-inclusive and pre-tax figures: ad spend and sale value should both exclude sales tax.
  • Calculating maximum CPA from revenue instead of gross margin.
  • Judging a campaign on a handful of conversions: below 30, CPA swings a lot.
  • Ignoring customer lifetime value, and cutting a campaign that pays off over time.

To size the spend, use our Google Ads budget calculator; to find what a customer is worth, our LTV calculator; and to check your margin, the margin calculator. Our glossary entry on ROI completes the picture, and how much Google Ads costs a small business gives real budgets. If you would rather hand it off, here is how we manage Google Ads.