US to UK Kids' Clothing Size Conversion
| US Age | UK Age |
|---|---|
| 2T | 2-3 |
| 3T | 3-4 |
| 4 | 4-5 |
| 5 | 5-6 |
| 6 | 6-7 |
| 7 | 7-8 |
| 8 | 8-9 |
Sizing conventions vary by brand and by cut — this table shows the standard published conversion. Always check the garment's own size chart when one is available. See how these tables are compiled.
A gift or a school-uniform order is the usual reason for this direction
This conversion mostly comes up two ways: sending a gift to a child in the UK, or an American family relocating and suddenly needing to buy into UK school-uniform sizing for the first time. Both situations share a practical wrinkle age-based conversion alone won't solve — you're often buying without the child in the room to check anything against.
Major UK high-street chains (Marks & Spencer, Next, and similar) publish their own age-plus-height tables rather than a single flat age number, precisely because a straight US-age-to-UK-age conversion undersells how much two children of the same age can differ. Search that specific retailer's own kids' size guide rather than treating this page's conversion as the final word for a UK uniform order.
UK school uniform has its own separate sizing logic entirely
UK primary and secondary schools generally specify uniform items — polo shirts, jumpers, pinafores — sized by a UK retailer's dedicated schoolwear range, which runs on the same height-and-age chart as that retailer's everyday clothing but is cut with more room deliberately, since a uniform garment is expected to be worn for a full school year of growth, not just a season. Sizing up from a straight US-to-UK conversion is standard practice for uniform specifically, not a sign the conversion itself is wrong.
A converted UK size is still worth checking against a height chart before you order
If you have even an approximate recent height for the child, use it: most UK retailers publish height bands next to the age label specifically because parents ordering without trying garments on need a second data point beyond age. A US size 8 converting to a UK age 7-8 is a reasonable starting search, but a stated height puts you within that band more precisely than the age number alone can.
British winter ranges assume a different base layer
A British kids' winter coat or jumper is often cut assuming a school jumper or thermal vest underneath as a matter of course, in a way a typical American puffer-and-tee combination doesn't assume — a US shopper converting a size for a UK winter item may find it looser than expected if they're picturing it worn the way an equivalent American piece would be layered.
Frequently asked questions
Should I buy UK school uniform directly, or convert my child's US size?
Use the specific school's uniform supplier chart if one is named — most UK schools contract a particular retailer or supplier for uniform, and that supplier's own age-and-height table is more reliable than a general US-to-UK clothing conversion for uniform items specifically.
Is it normal for UK uniform to run larger than a converted everyday size?
Yes — uniform is deliberately cut with growing room to last a full school year, so sizing up from the general conversion is expected practice, not a sign you converted incorrectly.
I don't have the child's exact current height — what should I do?
Ask whoever last measured them (a parent, school nurse record, or recent pediatrician visit) for even an approximate recent figure — a height from several months ago is still more useful for a UK height-banded chart than guessing from age alone.
Will a UK winter coat run big if I convert my child's US size directly?
Possibly — British winter outerwear is often cut with a school jumper or thermal layer in mind underneath, so a converted size can feel roomier than an equivalent US puffer jacket worn over just a T-shirt.
Is gifting clothing to a UK child riskier than gifting to a US child?
A bit, mainly because you can't fall back on a shared reference size the way you could buying for a US child — err toward the retailer's stated height band over the age label alone, and consider a gift receipt or exchange-friendly retailer given you likely can't check fit in person first.
Do UK sizes for babies and toddlers follow the same age-based logic?
Broadly yes, though the youngest UK ranges are labeled in months rather than years and shift size more frequently — expect to size up faster for an infant gift than for an older child's converted size.