Guide
Exam photo size requirements: dimensions and KB limits explained
Exam notifications describe the photo in a mix of units — millimetres, pixels, DPI and kilobytes — and it is easy to confuse them. Once you see how they relate, any exam's photo specification becomes readable at a glance. This guide unpacks each unit and shows how to convert between them.
Pixels: the size the screen sees
Pixels are the individual dots that make up a digital image. A specification like “200 × 230 pixels” means 200 dots wide by 230 tall. This is the unit that actually matters for a web upload, because the portal stores and displays your photo in pixels. If an exam gives you a pixel size, resize to exactly that.
Millimetres: a print size in disguise
“35mm × 45mm” is the classic passport-photo size — a physical print measurement. To turn it into pixels you need the DPI (see below). The standard passport photo of 35 × 45 mm at 300 DPI works out to roughly 413 × 531 pixels. If an exam only gives millimetres, it usually also states a DPI, or you can safely assume 300 DPI for a print-quality photo.
DPI: the bridge between mm and pixels
DPI (dots per inch) tells you how many pixels fit into one inch of print. The conversion is simple: pixels = (millimetres ÷ 25.4) × DPI, since one inch is 25.4 mm. So 35 mm at 300 DPI is (35 ÷ 25.4) × 300 ≈ 413 pixels. Higher DPI means more pixels for the same physical size — which is why the same “35 × 45 mm” photo can be asked for at different pixel sizes by different exams.
Kilobytes: the file-size cap
Kilobytes (KB) measure how much space the saved file takes, which is separate from its dimensions. An exam that says “20–50 KB” is capping the file, not the picture size. You control KB through dimensions (fewer pixels, smaller file) and JPEG compression. Our dedicated file-size guide covers how to hit an exact KB target.
Putting it together
A complete photo spec has three parts: dimensions (in pixels or millimetres + DPI), a file-size window in KB, and a format (usually JPG). Read them in that order — get the dimensions right first, then compress into the KB window, then confirm the format. A signature spec is the same idea with smaller numbers and a wider, landscape shape.
You don't have to do the maths
Every exam page in Exam Photo Toolkit already encodes that exam's exact dimensions, KB window and format, so you never have to convert units by hand — pick your exam and the tool applies the correct numbers. Browse the full list of supported exams on the home page, or read why uploads get rejected to avoid the other common pitfalls.