Payback period
How many months a customer takes to repay what you spent winning them — the speed at which growth returns its own cash.
Payback period is how long a customer takes to return the cost of acquiring them: acquisition cost divided by the gross profit they generate each month. Twelve months of payback means a year of your money financing a customer before they fund anything else.
It is the constraint that lifetime value quietly ignores. A ratio of five to one looks excellent and can still bankrupt you, because lifetime value arrives over three years and the acquisition cost is paid this month. A business with a two-month payback can reinvest six times a year; one with a twelve-month payback reinvests once, and needs outside money to grow at the same speed. Same margin, entirely different company.
It also sets the honest ceiling on ad spend. If cash on hand can carry three months of payback and no more, then the acquisition cost you can afford is fixed by arithmetic, not by ambition, and it does not matter how good the long-run return is.
Worked: $600 to acquire, $100 a month of gross profit — six months to payback. On $60,000 of cash you can carry roughly 100 customers in flight. Cut acquisition cost to $400 and payback falls to four months, which lets the same cash fund 50% more growth without a dollar of financing.
Also known as
- CAC payback
- months to recover
Relevant for
- Founders
- Payback, not lifetime value, is what decides how fast you can grow without outside money — a strong ratio with a twelve-month payback is a fundraising plan.
- Business owners
- Work out how many months of winning a client your cash can carry at once; that number, not the ambition, is the real cap on what you can spend to grow.