The question is not "can we live on one income"
Couples usually frame this as: could we survive on the larger salary alone? That question is answerable but incomplete, because it ignores what the second income costs to earn, what it protects against, and what giving it up does to the years after the decision.
Three separate calculations, and most couples run only the first.
What a second income actually contributes
A second income does not arrive whole. Some of it exists only to make itself possible: childcare during working hours, commuting, a second car, work clothes, convenience food bought because nobody has time to cook. Those costs appear in the household budget as ordinary shared expenses, which is exactly why they never get subtracted from the salary that causes them.
To size a second income honestly, compare the household's disposable money in each scenario — what is left after shared costs — not the salaries.
The €1,900 that adds €1,200
Take a household with incomes of €3,200 and €1,900, and €2,600 of shared monthly costs, €700 of which is childcare needed only because both parents work. Combined income €5,100, shared costs €2,600, and the household keeps €2,500.
Now remove the second income. Household income falls to €3,200 — but shared costs fall too, to €1,900, because the childcare line disappears with the job. The household keeps €1,300.
The second salary is €1,900 on the payslip. Its actual contribution to the household is €1,200. Add commuting, a second car or work-driven spending and the gap widens further; in households with more than one child in paid care, the net contribution can approach zero.
That is not an argument for either choice. It is an argument for doing the subtraction before arguing.
Where the arithmetic turns the other way
Two things push hard in the opposite direction, and both are invisible in the monthly figure.
Risk. One income is a single point of failure. If it stops, nothing arrives — there is no second engine. That is why a one-income household needs a bigger emergency fund even though it spends less. On the numbers above: the two-income household targets four months of its €2,600 costs, or €10,400. The one-income household targets six months of its lower €1,900 costs — €11,400. Cheaper household, larger buffer.
Time. Career gaps compound. In most systems, retirement entitlement is built from contributions tied to earnings, so a break reduces the eventual pension as well as the current salary. Re-entry usually happens at a lower level than the exit, and the earnings curve stays flatter for years afterwards. The monthly comparison above is a snapshot; the decision runs for decades.
The options that get skipped
The debate is usually posed as full-time or nothing, and the useful answers are in between.
- Part-time. Often keeps the majority of the net contribution because childcare hours fall faster than salary does.
- Staggered hours. Two parents on shifted schedules can cut paid-care hours substantially without either leaving work.
- A defined pause. A break with a planned end date, and an agreed plan for keeping skills and contacts alive, is a very different financial object from an open-ended one.
Decide it as a household, not as a favour
If one partner steps back, the household gains their unpaid work and loses their earnings and future entitlement. The fair response is to recalculate the contribution split on the new incomes and to treat retirement saving for the non-earning partner as a shared household cost, not as a gift. Both are ordinary budgeting decisions once you say them out loud.
Run both scenarios
Put each scenario into the couple budget planner — two incomes with childcare in the shared costs, then one income without it. The difference in what the household keeps is the real number. Then size the buffer for the riskier of the two with the emergency fund calculator.
The related decisions
The child-cost side is covered in the real cost of a child, and the buffer question in one emergency fund or two.