CAC formula & calculator for ecommerce

The CAC formula is total customer acquisition cost ÷ new customers acquired in the same period. Worked example: with ₹1.2 lakh of acquisition costs and 200 verified first-time customers, CAC is ₹600 per customer.

Count unique first-time buyers and match their acquisition costs to the reporting period. Keep media-only cost in its own row. Use fully loaded CAC for the complete acquisition budget.

How to calculate CAC for ecommerce

Choose a completed reporting period, collect the acquisition expenses for that period and count the people who made their first purchase. Divide the first total by the second. Keep the customer definition unchanged when comparing months.

Shopify's July 2026 ecommerce acquisition guide describes acquisition around first-time customers. Its customer acquisition cost guide explains the cost-to-new-customer calculation and the need to include relevant marketing and sales expenses.

For a fully loaded view, include the acquisition share of your team's pay, agency services, creative production and tools alongside media spend. Assign shared costs using a documented rule. A retention specialist's whole salary should not move into acquisition just because the person sits in the marketing team.

For a paid media view, enter the media cost supporting acquisition and label the output accordingly. Record the acquisition allocation in the input worksheet so the buying team and finance use the same cost base.

Worked example: calculating a ₹600 CAC

The example ecommerce business is reviewing a completed month. It records the following costs allocated to acquiring new customers:

The order export shows 200 unique people making their first purchase. CAC is ₹1,20,000 ÷ 200 = ₹600. If the business reports only media spend, its media cost per new customer is ₹80,000 ÷ 200 = ₹400.

The ₹400 media figure tracks ad buying. The ₹600 fully loaded CAC includes creative production, agency work, team time and software. Compare each with the same cost scope in the next reporting period.

Suppose the same store processed 300 orders in the month. Dividing ₹1.2 lakh by 300 gives ₹400 per order. That result cannot replace CAC because some orders came from existing customers, and some people may have bought more than once.

Keep both rows if the team uses both decisions. Cost per order helps with fulfilment and current order contribution. Cost per new customer helps with acquisition economics and cohort repayment.

How to verify the new-customer count

Begin with the store's order history. Identify each customer's first qualifying purchase date, then count customers whose first purchase falls inside the reporting period. A person placing several orders in that window counts once.

Use a stable customer identifier. A person changing email addresses or buying as a guest can make customer matching difficult. Apply the same matching rule each month and investigate material changes before attributing them to the campaign.

Choose a treatment for cancelled and fully refunded first orders. For a retained-customer view, remove customers whose only qualifying purchase was cancelled or fully refunded. Track the reporting cut-off because a recent purchase can change status later.

A zero in an imported new-customer column requires a check. It may mean there were no new buyers, or it may mean that the source never supplied customer classification. Confirm against order history before dividing. Do not silently substitute total orders to make a result appear.

For COD, placed orders and retained buyers answer different questions. If acquisition planning depends on delivered, collected orders, use that status consistently. Keep the pending-delivery population separate so an incomplete recent month does not appear to have unusually poor acquisition efficiency.

Which costs should go into CAC

Use a cost ledger with an acquisition allocation column. Media invoices are straightforward, but mixed campaigns and shared services need a rule. For example, a creative shoot that supports both prospecting and existing-customer campaigns should not be charged twice across the two programmes.

Recurring agency fees and team costs should use the same allocation basis each period. A changed allocation deserves a note beside the chart. Otherwise the team can spend a meeting explaining a movement caused by bookkeeping rather than trading.

Keep discounts consistent with your contribution model. If an acquisition discount already reduces net revenue used to calculate contribution, do not subtract that same discount again as an extra acquisition expense when comparing contribution with CAC. Record where the incentive enters the model.

Recoverable taxes and tax-inclusive invoices also need consistent treatment. Use the expense basis agreed for the worksheet and have your accountant confirm recoverable tax treatment before adding invoices to the cost total.

Keep a second line for unusual launch expenditure if it makes month-to-month interpretation clearer. A product launch can incur costs before it produces first purchases. Showing both the actual-period total and a clearly explained longer-window view is more useful than hiding the launch bill.

CAC versus CPA and ROAS

A platform CPA divides platform spend by the conversions selected in its report. Those conversions may include returning-customer purchases or actions that are not purchases. It cannot automatically tell you fully loaded new-customer acquisition cost.

ROAS divides attributed purchase revenue by ad spend. It can improve because order value rises, even when the cost of acquiring each customer also rises. Use the ROAS calculator for that revenue ratio and keep it beside CAC rather than substituting it.

For a first-order acquisition ceiling, work out contribution on the first retained order. Subtract product, payment and fulfilment costs from net revenue. The resulting rupees are available to pay for acquisition before any reserve for overhead or profit.

Compare like costs. If you compare fully loaded CAC with a contribution ceiling, that ceiling must be able to pay all acquisition costs in the numerator. A media-only budget ceiling cannot be treated as permission to spend that amount on ads and then add agency and creative costs on top without checking the remainder.

How to calculate CAC payback

Payback asks when contribution from an acquired customer covers acquisition cost. Revenue alone does not repay acquisition: some of it pays for the products and delivery on each order.

Continue the worked example with ₹600 CAC. Suppose the first retained order contributes ₹450 before acquisition. The unrecovered amount is ₹150. A later order contributing ₹200 brings cumulative contribution to ₹650, which covers the original ₹600.

Payback occurs when the later contribution is realised. Measure cumulative contribution across the entire acquisition cohort, including customers who never buy again. Keep the original acquisition month as the cohort label.

For stable monthly contribution per acquired customer, CAC divided by monthly contribution per customer gives a payback period in months. Ecommerce repeat orders are often uneven. A cohort table showing cumulative contribution by elapsed month makes the repayment path easier to inspect.

Do not build the budget on a payback window the cash balance cannot support. Product purchasing, delivery charges and acquisition bills may fall due before the repeat purchase that makes the cohort profitable.

A worksheet for your next acquisition review

Create one row per reporting window with acquisition cost, verified new customers and CAC. Add columns for the share of orders still pending delivery and the cut-off used for refunds. Keep media-only cost in a separate field if the buying team needs it.

Then add the first-order contribution and cumulative cohort contribution available to repay acquisition. The profit margin calculator helps inspect the cost base before making that comparison.

For the live calculator, zero acquisition cost with verified customers returns ₹0. Zero customers produces no usable CAC, so the tool asks for a positive whole count. Fractional customers and negative costs are rejected. A result based on incomplete customer history should wait for a reconciled count before entering a budget decision.