How we check sizes

Where the numbers come from

1. The brand's own size chart page first. We copy each size's height and weight range (and waist, chest, foot length or head size where the brand lists them) exactly as published.
2. A retailer's copy only when the brand's chart can't be read. Some brands post their chart as an image. In that case we use a boutique or department store that reproduces the brand's chart, and we mark it below so you know.
3. No guessing. If we can't find numbers we trust, the brand isn't added. Monica + Andy, Primary, Little Sleepies, Colored Organics, Juddlies, Noppies and Nest Designs are waiting for confirmed charts.

How often we recheck

We recheck every brand's chart at least twice a year, and whenever a reader tells us a size looks wrong. Each result shows the date its data was last checked. Brands do change their charts, so for an expensive purchase, glance at the brand's own page too; every result links to it.

How the calculator picks a size

• We find the size that fits your baby's weight and the size that fits their height.
• If they point to different sizes, we choose the bigger one. A size that's a little roomy still fits; one that's too short in the body won't close.
• If a brand has its own chart for a type of clothing (for example Carter's pants, which uses waist), we use it. Otherwise we use the brand's general chart and say so on the result.
• Brands that size by height only, like H&M, are matched on height only.

How the forecast works

When you add your baby's age, we compare their weight and height today with the World Health Organization child growth standards for that age. We then assume they stay on the same growth curve, and read off their likely weight and height at later ages. That gives the "Buying for 9 months?" answer and the size timeline.

Babies grow in spurts, so treat forecast dates as estimates, especially more than six months ahead. Without an age, we use the WHO average for each age instead.

Sources for each brand

Found a mistake?

Email [hello@yourdomain.com] with the brand, size and what you saw on their chart. We check every report and fix confirmed errors within a week.