Living on One Income Calculator

Couples ask this before parental leave, before caring for a relative, before a sabbatical, and after a redundancy notice. The test is one subtraction: essential monthly spending against a single income. On the defaults here, a larger income of 3,000 against 2,500 of essentials leaves 500 a month, which is positive but thin. Push essentials to 3,200 and the same household is 200 short.

A worked example

With the defaults of income A at 3,000, income B at 2,000 and essential monthly spending of 2,500, the tool returns 500.00. Change income A to 4,500, income B to 1,200 and essentials to 4,200, and the larger income clears the costs by 300 a month. Both results are positive, and both leave very little for anything that is not on the essentials list.

Which income stops matters

The primary figure uses the larger of the two incomes, so it answers a narrower question than the tool name suggests: can this household run on its best single income? On the defaults that is a 500 surplus. Keep the smaller income instead and the same household is 500 short every month, because 2,000 does not cover 2,500 of essentials. The Balance on Smaller Income row carries that second figure, so the answer does not depend on which income the reader assumed would stop.

Which income pauses is often not a free choice. Redundancy, illness and caring duties land where they land. Research on how households absorb a lost income, including the NBER paper on worker displacement and the added worker effect, tracks the remaining partner's working hours before and after the job loss and reports responses that are larger after the displacement than before it, persistent over time, and bigger where the lost wage was bigger.

What counts as essential

Essential spending here means housing, utilities, food, insurance, transport to work, minimum debt payments and basic childcare. Everything else counts as discretionary for this test, which is the point of it: discretionary spending can be cut, so the viability question is about the floor. Where that floor sits varies by country and by household size. The ILO's living wage work estimates the needs of workers and their families for wage-setting purposes and uses much the same categories.

When this metric matters most

• Planning for a career break, extended leave, or a shift to part-time work
• Testing household resilience against the loss of either income
• Modelling a transition before it happens, so spending adjustments surface early
• Sizing the gap between current two-income spending and single-income reality

What the result does not show

The calculator shows the monthly difference between an income and essential spending. It does not show:

• Non-essential spending such as entertainment, gifts, hobbies and subscriptions
• Irregular or seasonal costs such as vehicle maintenance, annual renewals and travel
• Changes to income from reduced hours, variable earnings or a different tax position
• Changes to essential spending such as school fees, childcare or health costs
• Savings, debt repayment beyond the minimum, or investment contributions
• The timing and sequence of a transition, which decides how long any gap has to be covered

For educational illustration only

This calculator models a snapshot from the figures entered. Real situations move: incomes change, essential costs change, and the timing of a transition changes what the household needs in the months around it. The output is an estimate for discussion, not a forecast.