Baby Clothes Size Calculator
Which baby clothes size fits — by weight and length rather than age — with UK/EU centimetre sizes, US age labels and how long until the next size up.
How it works
Pick the smallest size whose weight AND length limits both cover the baby; EU sizes are the garment length in cm
Age labels on baby clothes are a rough proxy — a 6-month-old can wear anything from 3–6 to 9–12 months. Manufacturers actually cut to weight and length bands, so measuring gives a much better fit. European sizing (56, 62, 68…) simply states the height the garment fits in centimetres, which is why it is the easiest system to shop across brands. Babies roughly double their birth weight by five months and triple it by a year, so sizes turn over fast early on.
Worked example
6.5 kg and 62 cm is at the top of 0–3 months (EU 62); 3–6 months (EU 68) is the sensible buy and will fit within a couple of weeks.
Frequently asked questions
Should I size up for sleep?
Sleepsuits and bodysuits shrink and need room for a nappy — one size up is comfortable; avoid loose necklines and cords for safety.
How many newborn outfits do I need?
Few — many babies are in 0–3 months within a fortnight. Six to eight newborn bodysuits and sleepsuits is plenty.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.