How to Resize a Photo in cm (With the Right DPI)

Ask a form for a photo “3.5 x 4.5 cm” and you’ve asked for a physical size. A phone photo has no centimetres in it, only pixels. To resize a photo in cm you need one more number, the DPI, which says how many pixels make up each inch of paper. Get that number wrong and the file comes out tiny, or the portal rejects it. Below are the formula, worked pixel sizes for the common Indian document sizes, and how to do it in ResizeAny.

Quick answer: To resize a photo in cm, convert to pixels: cm ÷ 2.54 × DPI. A 3.5 x 4.5 cm photo is 413 x 531 px at 300 DPI or 276 x 354 px at 200 DPI. A PAN card photo (2.5 x 3.5 cm at 200 DPI) is 197 x 276 px. Use the DPI your form gives; for prints with no rule, use 300.

Why centimetres need a DPI

Screens and upload portals count pixels. Paper is measured in centimetres or inches. DPI (dots per inch; for digital files it really means pixels per inch) is the link between them. One inch is exactly 2.54 cm, so the formula is:

pixels = cm ÷ 2.54 × DPI

Take a 3.5 cm width. At 300 DPI that’s 3.5 ÷ 2.54 × 300 = 413 pixels. At 200 DPI it’s 276. Same centimetres, different file. Both are correct; they’re just made for different jobs.

That’s why “resize to 3.5 cm” with no DPI is an incomplete instruction. When the DPI box is empty, ResizeAny falls back to 96 DPI, an old screen convention, and a 3.5 x 4.5 cm photo then becomes 132 x 170 pixels. That’s too small for most portals and looks soft in print.

Photo sizes in cm converted to pixels

The pixel columns are my own arithmetic using the formula above, rounded to the nearest pixel, the same way ResizeAny rounds them.

Note that 5 x 5 cm isn’t quite a US visa photo. The State Department asks for 2 x 2 inches (51 x 51 mm), which at 300 DPI is exactly 600 x 600 px, its digital minimum. A 5 cm square at 300 DPI lands at 591, just under. And the PAN numbers only make sense at 200 DPI, because that’s the resolution Protean names.

What forms actually check

Read the notice before you pick a DPI, because forms check different things.

Some give cm and a DPI. Protean’s guidelines for DSC-based PAN applications ask for a 3.5 x 2.5 cm colour photo and a 2 x 4.5 cm signature at 200 DPI, in JPG, up to 20 KB and 10 KB. Here the cm and DPI together fix the pixels, and the details are in our PAN card photo and signature size guide.

Some give pixels and only mention cm in passing. Several IBPS scanning guidelines, such as the PSB March 2026 notice, prefer a 200 x 230 pixel photo and a 140 x 60 pixel signature, scanned at 200 DPI or more. Other IBPS notices ask for 240 x 240 pixels at 200 DPI, roughly 3 x 3 cm. If a notice gives pixels, type pixels and ignore the cm.

And some ask for a print in cm but a different pixel size for upload. Passport Seva tells applicants to carry two 4.5 x 3.5 cm colour photos on a white background. Its ICAO photo guidelines, though, ask for a 630 x 810 pixel digital image. That’s the same 7:9 shape as 3.5 x 4.5 cm, at about 457 DPI. Nobody measures the centimetres of an uploaded file; the portal checks pixels and KB.

So the rule of thumb: if the notice gives pixels, use them. If it gives cm and a DPI, use both. If it gives only cm and you’re printing, use 300 DPI.

How to resize a photo in cm with ResizeAny

1. Open the resize image in cm tool and drop in your photo. For a fixed size, start from a preset instead: 3 x 4 cm (300 DPI), PAN card photo (2.5 x 3.5 cm, 200 DPI, 20 KB target) or 5 x 5 cm. More are listed under exact sizes in cm.
2. Check the DPI box before anything else. ResizeAny uses the number you type there to turn cm into pixels. If the box is empty, it converts at 96 DPI. The 5 x 5 cm preset leaves it empty, so type 300 (or 200 if your form says so).
3. Type the width and height in cm, with cm selected as the unit.
4. Under Ratio & fit, pick Crop if your photo’s shape doesn’t match the target. Presets with both sizes start on Stretch, which forces the exact size and can squash a face. For a portrait you may prefer the crop tool: 3:4 matches 3 x 4 cm and 5:7 matches 2.5 x 3.5 cm. There’s no 7:9 button for 3.5 x 4.5 cm, so use freeform there.
5. Download as JPG or PNG. ResizeAny writes the DPI into both, so print software reads the photo at the size you chose. WebP and AVIF files don’t carry it.

If the result is over the form’s KB limit, add a target file size, or see how to reduce an image to 50 KB. The photo is processed in your browser and never uploaded.

Printing at the right size

A wrong-size print is often the print dialog’s fault, not the file’s. Choose 100%, “actual size” or “no scaling”. “Fit to page” stretches a 3.5 x 4.5 cm photo to fill the sheet. If the DPI in the file doesn’t match the one you converted at, the printer gets it wrong too: a 413 x 531 px photo saved at 96 DPI prints at about 10.9 x 14 cm.

Check whether you’d be enlarging, too. Turning a small 300 x 400 px crop into 3.5 x 4.5 cm at 300 DPI works, but it can’t add detail the original never had. Start from the camera’s original, not a copy that has already been shrunk. For bigger prints and the DPI-versus-viewing-distance question, see image size for printing.