Quit your job to start a business when your side income hits your quit number: monthly recurring revenue at 1.2 times your post-tax salary, or savings that cover your growth timeline plus two months — with a 6–12 month cushion you never touch. Not a feeling. Not "a lot." A specific euros-per-month figure you know cold.
Picture a founder we'll call Sarah. Her side business had paid her more than her corporate salary for three months in a row — €8,200 in MRR against €7,400 post-tax — with €38,000 in savings, untouched. She resigned that morning, and it didn't feel like a leap. It felt like the inevitable next step, because the decision was the result of the math. Here is the math.
When to quit your job: the three quit-number formulas
The quit number is the threshold of side-business performance that gives you permission to walk away from your salary without burning your life down. There are three valid formulations, and most founders end up using a hybrid of two:
| Formula | The math | Best for |
|---|---|---|
| MRR replaces salary | MRR = post-tax salary × 1.2 | Steady businesses already near replacement income |
| Savings cover the runway | Runway exceeds the growth timeline by ≥ 2 months; growth consistent for ≥ 3 months | Fast-growing businesses not yet at replacement |
| The hybrid | MRR at 60–80% of replacement + 6–12 months of runway + consistent growth | Most founders |
Formulation one is the simplest: when MRR equals your post-tax monthly salary, you can quit. But MRR isn't take-home — you have business expenses, taxes work differently, the cushion has to be built — so the version most founders use in practice is salary times 1.2. If your post-tax salary is €7,400, your quit threshold is €8,900 in MRR. The 20% buffer absorbs the gap between gross revenue and personal take-home.
Formulation two works when growth is fast but income hasn't caught up. Say you have €40,000 saved and living expenses of €4,000 a month: ten months of runway. Your side business is at €4,000 MRR, growing €500 a month, so you'd hit your €8,000 replacement number in eight months. Eight months of growth, ten months of runway, a two-month buffer. You can quit — as long as the runway exceeds the growth timeline by at least two months and the trajectory has been consistent for at least three.
Formulation three combines them: MRR at sixty to eighty percent of replacement, six to twelve months of runway saved, growth consistent. Each piece covers for the others — the MRR floor catches you if growth stalls, the savings catch you if MRR drops. All three should be green before you quit.
The partner-income rule
None of these formulas include your partner's income. If your partner earns, their salary changes the math in one direction only: it extends your runway. It does not lower your MRR threshold. A side business that depends on your partner's salary to survive is not yet a real business; it's a hobby that draws from a shared bank account. Build to the number that lets you stand alone — then enjoy the fact that you don't have to.
Sit down with these formulations this week. Write your quit number on paper and tape it somewhere you'll see it daily. An exact figure is what separates founders who quit cleanly from founders who agonise for an extra eight months because they never decided what enough actually was.
The savings cushion is non-negotiable
Even with the quit number hit, you need a savings buffer untouched on the day you resign: six to twelve months of full living expenses, in cash or near-cash, that you do not touch under any circumstances during your first year of full-time solopreneurship.
Revenue is volatile. The business at €9,000 MRR today might be at €7,000 in three months because a major customer churned, an experiment failed, or you got sick for two weeks. Without a buffer, a dip becomes a crisis. With one, it's a temporary annoyance — and it also covers what you don't know to plan for: tax obligations that hit harder once you're self-employed, a dying laptop, a flat-revenue quarter.
The discipline: build it separately while employed. Live on the corporate salary, and route side-business revenue into operations plus a separate account labelled "do not touch." The day you quit, the cushion stays where it is — insurance, not operating capital. Founders who treat it as available cash burn through it in four months and are back in corporate within a year. Founders who treat it as untouchable still have it three years in, which means three years of psychological calm in which to build something real. The good news: the building itself is cheap now — a production SaaS runs about €340 a month in tools, funded from your salary while you climb toward the number.
How to resign — and why you refuse the counter-offer
The resignation itself is mechanically simple and emotionally weighted. Give appropriate notice — two to four weeks for most professional roles, six to eight for senior or specialised ones. The relationships you preserve on your way out are the same ones that will refer you customers, partnerships, and consulting work in your first lean year.
Have the conversation in person, not by email. "I want to let you know I'm giving my notice. My last day will be [date]. I want to make this transition as smooth as possible." No over-explaining, no apologising — it lasts about three minutes if you let it.
Then be ready for the counter-offer, because about a third of resigning employees get one. A raise, a title bump, a role change. The counter-offer is not a sign you should stay. It's the company saying "we noticed too late that you were undervalued, and we're trying to fix it now that you've forced the issue." Decline politely: "I appreciate it. The decision is about what I'm building, not what I'm leaving." Then document everything and hand off cleanly — you want the colleague asked about you in six months to say "absolute pro, even on the exit."
Quit too early or quit too late: the two failure modes
Too early. A product manager we'll call Tom — an archetype, not a person — quit after a bad quarter with two months of savings, no validation, no buffer, no replaced income. The first three months were euphoric: MVP shipped in five weeks, three paying customers by week seven. But by month four he was at €400 MRR with savings running out. Month five, freelance contracts to extend the runway — thirty hours a week that stalled the product completely. Month eight, he was back behind a corporate desk, eleven months of life, savings, and momentum spent. Tom didn't fail because the idea was bad. He failed because he quit before the math told him to.
Too late. A senior designer we'll call Anna built a productized service to €14,000 a month with five retainer clients against an €8,000 salary, with €90,000 in savings. By every measure she could have quit a year earlier. She didn't — "one more buffer client," "what if the market changes" — because the real reason was fear that the identity she'd built over twelve years wouldn't survive the transition. She worked fifty hours for the agency and twenty-five for her clients until, exhausted and frequently sick, her partner sat her down: "You're not going to make it through another year like this." She quit a month later, having paid for the delay with a year of her life. When the math says go, go. If you want a structured path through that transition, it's exactly what the Solopreneur Accelerator is built around.
Frequently asked questions
What is a quit number?
The specific, quantified threshold of side-business performance that gives you permission to resign: typically MRR at 1.2 times your post-tax salary, savings covering your growth timeline plus two months, or a hybrid — MRR at 60–80% of replacement with 6–12 months of runway and consistent growth.
Should I count my partner's income in the math?
Only as extended runway — never as a lower MRR threshold. A business that needs your partner's salary to survive isn't a business yet. Build to the number that lets you stand alone.
How much savings do I need before quitting my job?
Six to twelve months of full living expenses in cash or near-cash, untouched on the day you quit and untouched through your first year. It's insurance, not operating capital — raiding it is how founders end up back in corporate within a year.
Should I accept a counter-offer when I resign?
No. About a third of resigning employees get one, and it's the company fixing an undervaluation only because you forced the issue. Decline politely and go. If what's really keeping you at the desk is fear rather than math, take the Corporate Suffocation Index and see the pattern for yourself.