TL;DR
Divide your fixed costs plus the salary you need by what each customer leaves you after fees and running costs. That number is your real target, and it is usually higher than founders expect. Check it before you quit, not after.
You have a product, a few users, maybe your first paying customers. The question that keeps coming back at night is simple: how many of them do I need before I can stop doing this on the side?
Most founders answer with a feeling. "A hundred customers should do it." The math is quick, and it rarely agrees with the feeling.
The three numbers you need
You only need three numbers to get a first answer.
- Your fixed costs per month. Hosting, tools, domain, accountant, insurance. Everything you pay whether you have one customer or a thousand.
- What you need to pay yourself per month. Before tax, the real amount that replaces your salary.
- What one customer leaves you per month. The price they pay, minus payment fees, minus what serving them costs you: API calls, storage, support time.
The third number is the one founders get wrong. A €19 plan does not leave you €19.
A worked example
Say you sell a plan at €19 per month. Your payment provider takes about 3%, and each customer costs you around €2 a month in API calls and storage.
- Margin per customer: 19 × 0.97 − 2 = €16.43
- Fixed costs: €150 per month
- Salary you need: €3,000 per month
Break-even, with no salary: 150 ÷ 16.43 = 9.1, so 10 customers.
To pay yourself: (150 + 3,000) ÷ 16.43 = 191.7, so 192 customers.
That gap between 10 and 192 is the whole story. Covering your costs is easy. Replacing a salary is a different business.
What the number tells you
Once you have your target, three questions become concrete.
- Is the market big enough? If your target is 192 customers and you can only name a few hundred potential buyers, you need almost all of them.
- Is the price right? Moving from €19 to €29 cuts the target by a third. Raising prices is often faster than finding more customers.
- Can your channels deliver it? At ten new customers a month, with nobody cancelling, you need well over a year to get there.
Run it on your own numbers
Use the calculator below with your real price and costs. If the result surprises you, that is the point: better to find out now than three months after quitting.
What this calculation leaves out
It ignores taxes, cancellations and what it costs you to win each customer. Those three can easily double the real target, which is why a full model counts them. Treat this number as a floor, never as a plan.
FAQ
Should I count taxes in the salary I need?
Yes. Use what you need to pay yourself before tax and social charges, not what lands in your account. Otherwise the target looks smaller than it is.
What about customers who cancel?
This calculation is a snapshot. If customers leave every month, you need to win new ones just to stay at the same number, so plan on acquiring more than the target.
Adrien Lebas
Founder of Banast, building it alone from Avignon. Writes about what it takes to make a living from what you build.