Tool 02 — See the whole month at once
Budgets break on surprises, not on totals. Most new parents can name the price of a box of diapers but not their monthly wipe burn, or how formula ounces peak around month five. This simulator uses transparent model prices (diapers 24¢, formula 19¢/oz as preset examples — change them to your real numbers) so the shape of the bill is right even before your exact prices are.
Defaults: diapers/day by age 11 / 9 / 8 / 7 / 6; formula ounces/day 24 / 28 / 24 / 20 / 8 before the feeding fraction is applied. Wipes model $17/month, basics $22/month. All figures are planning models, not quotes.
Formula is the biggest line for formula-fed babies — which is why the formula guide's per-ounce math matters more than any diaper hack. For breastfed babies the same month models near $106, with the difference mostly in the feeding line, not in love, effort, or outcomes.
Your baby's cost curve is not flat. Diaper changes fall from about eleven a day in the newborn weeks to about six after the first birthday, while food spending climbs from zero to fifty dollars or more. A single "babies cost $X a month" headline is therefore useless for an actual household budget. What works: rerun this simulator at every size change and every feeding change — five times in the first year — and adjust one line of your budget each time. Five small, calm corrections beat one panicked overhaul in month nine.
Also build the boring buffer. One extra big box of the next size (not three — see the stockpile ceiling in the diaper guide), one spare can of formula if you formula-feed, and two weeks of wipes. That buffer, roughly $80–$120 in model prices, is what stands between a normal Tuesday and a 31¢-per-diaper emergency run.
PR — SHOPPING SEARCH LINKS (NO AFFILIATE ID YET — SEE DISCLOSURE)