The honest question this calculator answers isn't whether your business idea is good. It's a narrower, more useful one: if you spend your hours doing this work, do enough of those hours come back as money for the work to be worth doing. That's not a question about ambition or markets or vision. It's a question about whether the labour pays for itself once Germany has taken its share.
What the model does
You enter what comes in: by customer, by month, or as a list of separate revenue items at different cadences. You enter what goes out: rent, software, accountant, staff, all the small monthly bleeds. The model strips VAT from the revenue, adds 22% Lohnnebenkosten to any staff costs, subtracts Gewerbesteuer above the €24,500 annual Freibetrag, and tells you what's left. The verdict box reads as a parallel income statement: what each month makes and what the year actually keeps after tax.
If you need a loan to get started, open the loan section and the calculator adds the monthly debt service to your fixed costs. The default rate uses KfW StartGeld's published maximum (about 5%, ten years, capped at €200,000), which is the programme most small new businesses qualify for. Real offers often come in lower.
Things the calculator surfaces that owners discover the hard way
The cost of a hire is not the gross salary
Lohnnebenkosten (the employer's share of pension, health, care and unemployment insurance) adds about 22% to whatever gross you put on the contract. A €3,000 gross hire actually costs the business €3,660 a month before they've earned their first euro for you. New owners almost always plan around the gross figure and then discover the gap when the first payroll runs.
Where you put your desk is a tax decision
Gewerbesteuer is set by the municipality, not the federation. Munich's Hebesatz is 490%, one of the highest in Germany; Berlin's is 410%; rural Bavaria can be 240%. On the same €60,000 of taxable profit, the Munich business pays roughly €6,100 in trade tax and the Oberpfalz business pays about €3,000. The Bundesland selector picks up the regional default. For most small operations the location is set by life, not by tax. But the gap is real and worth knowing.
A profitable business and a healthy business are different things
A business making €500 a month on €25,000 of revenue is profitable. It is also two percent margin away from disaster. The profit margin metric (what's left after costs as a share of net revenue) tells you how much room the business has to absorb a bad month. Healthy small businesses tend to run between 10 and 25 percent; tight ones run under 5. The verdict box gives you the profit number; the margin tells you whether that number is going to survive a slow week.
If you don't pay yourself, the customer is buying your time at a discount
A solo founder who runs the calculator with zero in the staff line will see a beautiful profit margin. They are also subsidising their customers with their own unpaid labour. The "max gross at break-even" hint next to the staff field is the honest read: at your current numbers, this is what the business could afford to pay you and still break even. If that figure is less than what you'd accept to do the same work for someone else, the business isn't really profitable yet. It's living on your willingness to be underpaid.
What the calculator doesn't model
It doesn't model the year, only the month. Seasonality, a slow ramp from opening day, the client who pays sixty days late, the supplier who raises prices, the quarter where you take on no new work because you're delivering a big project, the week you're too ill to invoice. None of that is here. The model assumes a typical month and scales it to twelve. Real years are messier.
It also doesn't tell you whether the demand assumptions are realistic. The calculator can say that 600 customers a month at €15 each pays for itself. It cannot say whether 600 customers a month is achievable in your neighbourhood. That part you work out with foot traffic, competitor counts, and conversations with people already running similar businesses.
Personal income tax happens after the business pays you out, and isn't included here. For that the salary you draw goes through the net salary calculator.
Using it
Run it once with your honest numbers, then change one thing at a time and watch what moves. A 10% price rise, a quieter month, an extra hire, a different city. The sensitivity table at the bottom shows a few of those moves laid out at once. Treat the numbers as a stress test, not a forecast. And especially not a decision. The decision is yours; the calculator just makes the consequences legible before you commit to them.