Leaving employment to run a business full time changes your financial life. A predictable salary is replaced by variable income, and costs that an employer covered, such as equipment, training, pension contributions or paid leave in many countries, become your responsibility. Before making the leap, a few calculations provide clarity and confidence.
These calculations are not complicated. They require honesty about your costs and realism about your income.
Your minimum monthly income
Start with what you need each month to live: housing, food, transport, insurance, debt repayments, family costs and other essential expenses. Add a reasonable amount for savings and occasional costs. This is your minimum personal income.
Then add business costs: software, equipment, marketing, professional fees, insurance and other operating expenses. Finally, allow for taxes and contributions that will no longer be deducted automatically. Ask an accountant to help estimate these for your situation.
The total is the monthly income your business needs to generate before you are financially stable.
Your savings runway
Your runway is how many months your savings could cover the gap between business income and your minimum needs. For example, if you need €3,000 a month, your business currently produces €1,800 and you have €12,000 in savings set aside for the transition, your runway is ten months.
A longer runway reduces pressure and gives the business time to grow.
The income gap
Compare your current side-project income with your minimum monthly income. The difference is the gap your business must close. Estimate realistically how much additional income full-time effort could produce, based on current demand, conversion rates and your capacity.
Avoid assuming that doubling your time will automatically double your income. More time often brings more administration and marketing work as well.
Your runway is how many months your savings could cover the gap between business income and your minimum needs.
Replace the hidden benefits
Employment often includes benefits that are easy to overlook: paid holidays, sick pay, pension contributions, equipment, training and sometimes health insurance, depending on the country. Estimate the value of these benefits and include them in your calculations.
Many independent professionals discover they need to earn more than their previous salary to be equally well off.
Plan for variability
Business income rarely arrives evenly. Some months will be strong; others will be quiet. Use your side-project history to understand seasonal patterns and plan for months below your average. Your buffer should cover these fluctuations.
Revisit the numbers regularly
These calculations are not one-time exercises. Update them monthly as your income, costs and savings change. Clear numbers help you decide when to proceed, when to wait and when to adjust your plans.
A simple decision table
Many founders find it helpful to write three numbers on one page: minimum monthly income needed, current average monthly business income and months of runway. If business income covers most of the minimum and runway is comfortable, the leap is far less risky. If income is low and runway short, it may be better to keep building before leaving.
Common mistakes
Founders often use their best month as a guide instead of their average, forget taxes and benefits, or count all savings as runway, leaving no emergency reserve. Being conservative in these calculations is not pessimism; it is protection.
An example in practice
A web developer earned an average of €2,200 a month from freelance work alongside his job. His minimum monthly income, including business costs and estimated taxes, was €3,400. With €18,000 of transition savings, his runway was fifteen months if income stayed flat. He reduced his employed hours first, then resigned when freelance income reached €3,000 for three consecutive months.