It is square, and that is not a detail
2 × 2 inches. Every camera you own produces a rectangle, so a US photo is always a crop, and it is always a crop that throws away more of the frame than you expect.
The practical consequence is at the top and bottom. Cropping a portrait photograph to a square takes the height down to the width, which means a picture framed comfortably for a UK photo will not contain enough above the head to make a US one. Stand further back than feels necessary.
The metric figure is a rounding of the imperial one
The specification is imperial and the millimetres are a conversion: 2 inches is 50.8 mm, published as 51. Working from 51 mm rather than 2 inches introduces a fifth of a millimetre of error, which does not matter on its own but does compound if you then compute the head range from it too.
If your printer speaks inches, give it inches. The conversion only exists for people whose tools do not.
There is a maximum pixel size, which is unusual
Between 600 × 600 and 1200 × 1200 pixels. Most countries publish only a floor, so a large file is safe; here it is not. A photograph straight from a modern phone is several thousand pixels on a side and will be refused for being too big until it is resized.
It is a strange rule to meet by accident, and it is the reason a US photo often needs a deliberate downscale where a UK one never does.
Eye height is a second, independent measurement
Your eyes must sit 1⅛ to 1⅜ inches (28–35 mm) above the bottom edge, in addition to the head measuring 1 to 1⅜ inches (25–35 mm) from chin to crown.
For most adult faces the second follows from the first, because eye level falls at a predictable fraction of head height. It stops following for children, whose faces occupy a different proportion of the head — which is why a child's photo can satisfy the head rule and fail the eye rule at the same time.
Printing several at once
A 51 × 51 mm photo is not a paper size anybody sells, so prints are produced several to a sheet and cut out. On 6 × 4 inch photo paper at 300 DPI, 2 fit in a 2 × 1 grid, each occupying 602 × 602 pixels of the 1800 × 1200 sheet. There is more on that, including the print setting that quietly ruins it, on the printing page.
Where these numbers come from
Verified on 2026-08-10 against travel.state.gov — Passport Photos . The dimensions live in one file in this project and are checked by an automated test on every change, so the tables above and the tool cannot disagree with each other. They can both be out of date, which is why the date is on the page and the source is linked.
Frequently asked questions
What size is a US passport photo?
2 × 2 inches, which is a square. In millimetres that is published as 51 × 51, though 2 inches is exactly 50.8 mm — the metric figure is a rounded conversion of the imperial specification, not the specification itself.
What size is a US passport photo in pixels?
Between 600 × 600 and 1200 × 1200. Note the maximum: unlike most countries the US publishes an upper bound, so an unmodified phone photograph is too large and must be resized down.
How big should my head be in the photo?
1 to 1⅜ inches (25–35 mm) from the bottom of the chin to the top of the head, inside a 2-inch square. That is a ten-millimetre window, twice as forgiving as the UK's five.
Why do my eyes have their own measurement?
Because head size alone does not fix where the head sits in the frame. The eyes must be 1⅛ to 1⅜ inches above the bottom edge, which pins the vertical position as well as the scale. In practice it follows automatically on an adult face and does not on a child's.
Is a US photo the same as a UK one?
No. The US photo is a 51 mm square; the UK photo is a 35 × 45 mm rectangle. Different shape, different head range, and different background colour — white for the US, light grey for the UK. Neither can be cropped from the other.