Cost of kids FIRE calculator: how many years did the toddler add?

By Tom, CPA · Updated October 25, 2026

TL;DR: Enter base spending, number of kids, annual cost per child, tax credits, how many years of kid costs continue after you reach FIRE, your return, withdrawal rate, portfolio and savings. The calculator shows the net annual kid cost, FIRE numbers with and without kid costs, and how many years children add to your timeline.

Educational only, not tax, legal, or investment advice. Examples are illustrations, not predictions. Rules and limits change; verify current figures and talk to a qualified professional about your situation.

Children are wonderful, expensive and very bad at budgeting. This calculator estimates, lovingly, how much they shift your FIRE date. It doesn't judge. It just does math, which is more than the toddler can say.

CPA Warning Label: This calculator measures dollars, not hugs. Results do not account for the value of sticky handmade birthday cards.

Inputs

• Base spending: what you'd spend per year in retirement without kid costs.
• Number of children and annual cost per child: use your own budget. As a reality check, the USDA's last Expenditures on Children by Families report estimated $233,610 to raise a child born in 2015 from birth through 17 in a middle-income, married two-child family, in 2015 dollars, excluding college.
• Tax credits per child: for 2026, the child tax credit is up to $2,200 per qualifying child under 17, as of October 2026. Early retirees with little tax liability or no earned income may get less, so enter what you'll actually receive.
• Years of child costs after FIRE: how long kids will still be on your budget once you stop working.
• Real return, withdrawal rate, portfolio, savings: standard FIRE inputs. Real return means after inflation.

Annual cost model

Net annual kid cost = (cost per child minus credits per child) times the number of children, floored at zero. The model assumes this cost comes out of your savings while you're working, so annual savings drop by that amount.

The FIRE number without kids is base spending divided by the withdrawal rate. With kids, the calculator adds the present value of the kid costs that continue after FIRE, treated as a fixed annual payment for the number of years you enter, discounted at your real return. Kid costs end, so they don't need a perpetual 25x multiple.

FIRE date shift

Years to FIRE solve the standard growth equation: the year your portfolio, growing at the real return with annual savings added, reaches the target. The calculator computes it twice:

• Without kids: full savings, base target.
• With kids: savings minus net kid cost, and the higher target.

The difference is "years added." If savings after kid costs are zero or negative and returns can't close the gap, the result shows 999, meaning the plan doesn't reach FIRE as entered.

Credits input

Tax credits soften the cost, but they depend on your situation. Key 2026 points, as of October 2026: the child tax credit is up to $2,200 per child under 17, phasing out above $200,000 of modified AGI ($400,000 joint); up to $1,700 is refundable if you have earned income above $2,500. Once you retire with little income, the nonrefundable part may not help much. The child and dependent care credit generally requires work-related expenses, so it usually ends at retirement. When in doubt, enter a lower credit for post-FIRE years. See FIRE with kids.

Example

Illustration. A couple spends $50,000 a year without kid costs, has two children costing $15,000 each, and gets $2,200 per child in credits. Kid costs continue 10 years after FIRE. Real return 5%, withdrawal rate 4%, portfolio $300,000, savings $60,000.

• Net kid cost: (15,000 - 2,200) x 2 = $25,600 a year
• FIRE number without kids: 50,000 / 0.04 = $1,250,000
• Plus present value of 10 years of $25,600 at 5%: about $197,676, for $1,447,676
• Years to FIRE: about 10.1 without kid costs vs. 15.8 with them: roughly 5.7 years added

Frugal Fran would point out that childcare often disappears when a parent stops working, so actual costs after FIRE may be lower than during the working years. Try a lower post-FIRE cost to see how that changes the answer. Lavish Larry would point out that his kids have a pony. That changes the answer too.

Limits

The model uses constant real costs and returns, ignores college (plan that separately with a 529), and treats credits as a flat amount. It doesn't model taxes on withdrawals, health insurance for a family, or a child's costs changing by age. It's a planning sketch, not a forecast. Rerun it as kids grow: the years-of-costs-after-FIRE input shrinks every birthday, and so does the gap.

If the result is discouraging, test levers one at a time: a lower post-FIRE cost, a few years of part-time income, or a slightly later FIRE date often closes the gap.