Family & Lifestyle · Family Changes
Living on One Income Calculator
Can we afford to lose a salary?
How This Calculator Works
Dropping from two incomes to one — for childcare, a career change, caregiving, or by necessity — is usually framed as "can we survive it," but the better question this calculator answers is "what does it actually cost, and is that cost sustainable indefinitely?" You enter the income that stays, the income that goes away, your joint monthly expenses, and any spending that disappears along with the second job — childcare being the classic offset, and often a startlingly large one.
The immediate outputs are the monthly gap or surplus on one income and, if there's a gap, your runway: how many months your current savings can absorb the shortfall before the plan breaks. A gap with a long runway can be a deliberate season; a gap with a short runway is a countdown. If one income covers expenses with room to spare, the model instead shows your one-income monthly surplus and what saving it steadily builds over time.
The long-view output compares retirement wealth on the two-income path versus the one-income path at your assumed return. That difference is the true price of the arrangement — not the lost salary itself, but the compounded value of the savings that salary would have generated. Seeing it as a concrete number lets a family weigh it against what the arrangement buys: years at home with kids, a parent cared for, a career rebuilt. The calculator prices the trade; it doesn't judge it.
Worked Example
Say the staying income is $95,000, the departing income is $60,000, joint expenses run $7,000 a month, and eliminating commuting and daycare cuts $1,800 a month of that. On one income, take-home pay against the reduced $5,200 of monthly expenses might land the household near break-even or a modest surplus — a very different picture from the panic the raw "$60,000 gone" framing produces. That's the calculation the childcare-offset slider exists to surface.
Now suppose expenses only fall by $800 instead: the same arrangement shows a persistent monthly gap, and the runway readout might show savings absorbing it for, say, two to three years. That reframes the decision as "this works if the second earner returns to work within the runway" rather than a simple yes or no. Meanwhile the retirement comparison quantifies the long-run side: several years of one income typically shows up as a meaningful but survivable dent in projected wealth at retirement — a number worth knowing before the decision rather than after.
Frequently Asked Questions
How do we budget to live on one income?
Start from the expense side, not the income side: separate your fixed obligations (housing, insurance, debt payments) from flexible spending, then identify what genuinely disappears with the second job — childcare, commuting, work wardrobe, convenience spending. The calculator's childcare-offset input captures the biggest of these. If fixed obligations alone consume most of the remaining income, the budget is fragile regardless of discipline; that's a structural signal, not a willpower problem.
How much does dropping to one income affect retirement?
The lasting effect comes less from the missing paychecks than from the missing contributions and their compounding — money not saved in your 30s is the most expensive money to replace later. The calculator's two-path retirement comparison shows the gap explicitly for your numbers and timeline. Families who protect even a reduced retirement contribution on the staying income typically close a surprising share of that gap compared to pausing saving entirely.
Does going to one income make sense when childcare costs almost as much as the second salary?
Sometimes, yes — when childcare, commuting, taxes, and work-related spending consume most of a second paycheck, the household's net gain from that job can be small, and the calculator makes that arithmetic explicit. Two caveats belong in the decision: the stepping-away earner also pauses retirement contributions and career progression, which are costs the monthly view doesn't show; and childcare costs end, while a career gap's effects can linger. Model both the current year and the years after childcare would have ended.
How big should our emergency fund be on one income?
Larger than it was on two. A dual-income household has natural redundancy — one job loss cuts income partially — while a one-income household's single point of failure argues for a bigger buffer, commonly toward the higher end of the usual several-months-of-expenses guidance. If the calculator shows a monthly gap being absorbed by savings, remember that the same savings are also your emergency fund: runway math that leaves nothing for genuine emergencies is optimistic runway math.
The model behind this calculator
spec v1.0.0 · 250 open casesThis calculator runs a published model: its inputs, formulas, assumptions, and exclusions are documented in a versioned specification, and it is Concordance-tested — an independent second implementation, built from that spec alone, must agree with it on 250 open test cases before any change ships. The same model is callable by AI assistants and developers.