CAC runway calculator

How the CAC runway calculator works

A new brand often pays more to acquire a customer than that customer is worth on the first order. This calculator shows how long that gap lasts and how much cash it burns. Monday Marketing Company looks at the total burn, not just the month the brand turns profitable.

The formula

CAC in month n = starting CAC × (1 − monthly improvement) ^ n
Gap per new customer = CAC − break-even CAC
Total burn = the deepest point of the cumulative cash curve, the sum of monthly losses before the first profitable month

Worked example

Illustrative numbers, not a benchmark. Starting CAC ₹900, break-even CAC ₹670, CAC improving 6% a month, 100 new customers a month. This example leaves out repeat purchase and fixed costs to show the mechanics.

CAC falls below ₹670 in month 5 (about ₹661), after about ₹41,000 of gap spend over the first four months. The full calculator also models repeat purchase, which is why the month the brand turns profitable usually sits later than the month CAC crosses break-even.

How to read the result

Focus on the total cash needed, not the month of profit. If the burn is larger than the brand can fund, the options are a lower starting CAC, a higher contribution per order, a stronger repeat rate or a slower ramp in new customers. Faster growth brings the profitable month closer but usually deepens the trough, so check the cash line before raising spend.

Growing faster usually deepens the trough, because more customers are acquired above break-even CAC each month. Repeat rate is the lever that shortens the burn, because repeat orders cost nothing to acquire.

Read the guide: what an order leaves behind, which sets break-even CAC · LTV:CAC calculator · D2C marketing glossary