Estimate diaper cost and usage over the years.
Diaper spending is a unit-price problem multiplied by a very large count. Seven a day across thirty months is well over six thousand diapers, so a two-cent difference in unit price moves the total by more than a hundred — which is why buying by unit price rather than pack price is the single effective saving. Usage falls sharply with age, from ten or twelve a day for a newborn to four or five for a toddler, so treating the daily figure as an average across the whole period keeps the estimate honest.
Total diaper cost
Diapers = per day x 30.437 x months; total = diapers x unit price + wipes per month x months
Around 2,500 in the first year and 6,000 to 7,000 across the full period. Newborns need ten to twelve a day, dropping to five or six by the first birthday and four by two years.
Over a full 30 months usually yes, but the saving is smaller than headline comparisons suggest once laundering, energy, and replacement inserts are counted. The break-even typically arrives around the first birthday.
Yes on unit price, with one caveat: babies outgrow sizes unpredictably, and a large unopened box of a size they have just left is a total loss. Buy bulk in the current size and singles in the next one up.