3 × 4 cm in pixels
A file stores pixels, and the DPI decides how large they print. With 2.54 cm to the inch, pixels = cm ÷ 2.54 × DPI. For the width, 3 ÷ 2.54 × 300 = 354.3, so 354 px. For the height, 4 ÷ 2.54 × 300 = 472.4, so 472 px.
| DPI | 3 × 4 cm in pixels | What to expect |
|---|---|---|
| 150 | 177 × 236 px | Small file for small uploads |
| 200 | 236 × 315 px | Light file, still clear on screen and in print |
| 300 | 354 × 472 px | Sharp prints (the preset) |
| 600 | 709 × 945 px | Extra detail and a bigger file |
In millimetres it is 30 × 40 mm. By convention “3 × 4” puts the width first, so the photo is 3 cm across and 4 cm tall. Some forms write the height first, as 4 cm × 3 cm: it is still the same upright photo.
Who asks for 3 × 4 cm photos
The 3 × 4 cm photo is everyday paperwork in several countries. Some examples from official sources:
- Brazil. “Foto 3x4” is the standard ID photo. The Espírito Santo state government, for instance, lists one recent 3x4 photo with a light background for a state identity card (RG). In Minas Gerais, the photo for the new national identity card is taken at the counter, and a 3x4 print is needed only for a baby in arms. (Espírito Santo, Minas Gerais)
- Indonesia. The Indonesian Health Council (KKI) asks health workers making some registration (STR) requests for a recent, formal 3x4 cm photo with a red background, as a JPEG of up to 200 KB. (KKI)
- Japan. University forms often use 4 cm × 3 cm. Hiroshima University, for example, asks for printed student ID photos 4 cm long and 3 cm wide. (Hiroshima University)
Notice how the background colour changes from one body to the next: light in Brazil, red for the Indonesian council. This tool keeps whatever background you photographed, so stand in front of the right colour when you take the picture. And whatever the examples say, the instructions on your own form come first.
3 × 4 cm is not the same as 3.5 × 4.5 cm
The two sizes look close, but they aren't interchangeable. A 3 × 4 cm photo is half a centimetre narrower and half a centimetre shorter, and its shape is slightly slimmer (3:4 against 7:9). Glue a 3.5 × 4.5 cm print into a 3 × 4 cm box and it hangs over the edges; trim it with scissors and you cut into the head or shoulders.
| Size | Shape | Pixels at 300 DPI | Resizer |
|---|---|---|---|
| 3 × 4 cm | 3:4 | 354 × 472 px | This page |
| 3.5 × 4.5 cm | 7:9 | 413 × 531 px | 3.5 × 4.5 cm resizer |
| 2 × 2 in (51 × 51 mm) | Square | 600 × 600 px | 2 × 2 inch resizer |
If a form only says “passport size”, find out which size the issuing country means before you print a sheet of copies.
Phone photos are often 3:4 already
Many phone cameras shoot in a 4:3 frame by default, and held upright that frame becomes 3:4: exactly the shape of a 3 × 4 cm photo. A 3024 × 4032 px photo, a common size, has those proportions, so crop to fill has nothing to trim and the whole picture is simply scaled down to 354 × 472 px.
That's convenient, but it also means your face stays as small as it was in the original. For an ID-style photo, your head should fill most of the frame. Two ways to get there:
- Crop closer first. Use your phone's crop tool at a 3:4 ratio, keep a little space above your head, then resize the cropped photo here.
- Position it with a guide. In the Passport Photo Maker, choose Custom size, enter 30 × 40 mm, then drag and zoom under the head guide. It can also print a sheet of copies.
Photos in other shapes, such as tall 16:9 shots or screenshots, are trimmed from the centre to fit, so check the top and bottom of the result in the preview.
Uploading a 3 × 4 cm photo with a size limit
On an upload form, centimetres only describe the shape and framing. The website itself checks pixels, format and kilobytes. If the form gives a KB cap, like the 200 KB in the KKI example, switch on Limit file size and enter that number. The 354 × 472 px size is kept and only the JPG quality drops, as far as needed.
For a lighter file from the start, choose 200 or 150 DPI: the shape stays 3:4 with fewer pixels. If the form gives exact pixel dimensions, switch to Pixels and type them in instead. To shrink a finished photo to a limit, there's also compress image to 200KB.
Printing 3 × 4 cm photos
Thanks to the saved DPI, a print app or Word places the photo at 3 × 4 cm without any guesswork. Print at Actual size / 100%, use photo paper for anything official, and measure one copy: it should be 30 mm across and 40 mm tall.
To fill a sheet with copies, make the photo in the Passport Photo Maker with a 30 × 40 mm custom size and download a 4×6 in or A4 sheet with cut guides. Any photo shop can print the 4×6 sheet as a normal photo print.