Newborns go through 10 or more nappies a day, and even toddlers use five or six. Most babies use roughly 2,500–3,000 disposable nappies in their first year. Sizes change with weight, so avoid stockpiling too many of the smallest sizes.
How to use the Diaper Calculator
- Baby’s age (diapers per day)
- Days to plan for
- Diapers per box
- Price per box
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose your baby’s age, the number of days to plan for, the diapers per box and the price per box.
Tips
- Use the figures printed on your product or its manual when you have them.
- Round quantities up so you are never short.
- Measure twice before you buy anything cut to size.
- Everything runs in your browser – try different values to compare options.
Common mistakes to avoid
- Mixing units (inches and centimetres, mAh and Ah).
- Ignoring efficiency losses and safety margins.
- Treating rules of thumb as exact.
Inputs explained
| Field | What to enter |
|---|---|
| Baby’s age (diapers per day) | Choose one: Newborn (≈ 11), 1–4 months (≈ 9), 4–8 months (≈ 8), 8–24 months (≈ 6.5) … |
| Days to plan for | A number |
| Diapers per box | A number |
| Price per box | Amount in your currency |
What each result means
- Diapers needed = ceil([Baby’s age (diapers per day)]×[Days to plan for] – 0.000001)
- Boxes = ceil([Diapers needed]÷[Diapers per box] – 0.000001)
- Cost = [Boxes]×[Price per box]
- Cost per diaper = [Price per box]÷[Diapers per box]
- Cost per year at this age = [Baby’s age (diapers per day)]×365.25×[Price per box]÷[Diapers per box]
Example values
How the main result changes when Days to plan for changes and everything else stays at the example values above:
| Days to plan for | Boxes |
|---|---|
| 15 | 2 |
| 22.5 | 3 |
| 30 | 3 |
| 37.5 | 4 |
| 45 | 5 |
| 60 | 6 |
Formula
Diapers per day by age: newborn 10–12, 1–4 months 8–10, 4–8 months 7–9, 8–24 months 6–7, 2–3 years 5–6Total = diapers per day × days; boxes = ceil(total ÷ diapers per box)Worked example
Inputs — Baby's age (diapers per day): Newborn (≈ 11); Days to plan for: 30; Diapers per box: 120; Price per box: $35.
Results — Diapers needed = 330; Boxes = 3; Cost = $105.00; Cost per diaper = $0.29; Cost per year at this age = $1,171.84.
Frequently asked questions
How many diapers does a newborn use per day?
About 10–12.
How many diapers in the first year?
Roughly 2,500–3,000.
Are cloth diapers cheaper?
Usually over time – a full set costs a few hundred dollars plus washing, versus $800–1,000 a year for disposables.
What formula does the Diaper Calculator use?
Diapers per day by age: newborn 10–12, 1–4 months 8–10, 4–8 months 7–9, 8–24 months 6–7, 2–3 years 5–6.