Crop Photo to Exact Size in cm (like 3.5 × 4.5 cm)
· ZapToolbox guides
To crop a photo to an exact size like 3.5 × 4.5 cm, do it in two steps: first crop the photo to the right shape (3.5 : 4.5, which is 7 : 9), then resize it to 3.5 × 4.5 cm at the DPI you need. At 300 DPI that is 413 × 531 pixels. Our free Crop Image and Image Resizer tools do both steps in your browser, and for passport photos the Passport Photo Maker does it all in one go.
This guide explains why a size in cm needs a DPI, gives a table of common sizes in pixels, and shows the steps on a phone or computer.
Why "cm" needs a DPI
A digital photo has no real size in centimetres. It only has pixels, like 3000 × 4000. A size in cm only appears when you print it or when a form decides how many pixels make one centimetre. That number is the DPI (dots per inch).
The formula is simple:
pixels = cm ÷ 2.54 × DPI
- 300 DPI is the usual setting for printing photos.
- Some online forms mention 200 DPI or another value. Use what the form says.
So "crop to 3.5 × 4.5 cm" really means "make the photo the 7 : 9 shape, and give it enough pixels for 3.5 × 4.5 cm at the DPI you need".
Common photo sizes in cm and pixels
| Size (width × height) | Shape | Pixels at 300 DPI | Pixels at 200 DPI |
|---|---|---|---|
| 3.5 × 4.5 cm (passport size) | 7 : 9 | 413 × 531 | 276 × 354 |
| 2.5 × 3.5 cm | 5 : 7 | 295 × 413 | 197 × 276 |
| 5.08 × 5.08 cm (2 × 2 inch) | 1 : 1 | 600 × 600 | 400 × 400 |
| 2 × 2.5 cm (stamp size) | 4 : 5 | 236 × 295 | 157 × 197 |
| 6 × 2 cm (signature strip) | 3 : 1 | 709 × 236 | 472 × 157 |
The sizes above are common examples, not official requirements. Use the size and DPI that your form or photo studio asks for.
Method 1: Crop then resize (any size)
Step A: Crop to the right shape
- Open Crop Image and choose your photo.
- Set "Aspect ratio" to Free.
- Type a Width and Height in pixels that has the shape you need. For 3.5 × 4.5 cm, use any pair in the 7 : 9 ratio, such as 700 × 900 or 1400 × 1800. Pick one smaller than your photo.
- Drag the box over the part you want, with your face centred and a little space above the head.
- Tap Crop image and download.
Cropping doesn't lose quality; it simply cuts away the parts outside the box.
Step B: Resize to the exact cm
- Open the Image Resizer and choose the cropped photo.
- Set Unit to Centimetres.
- Set DPI to 300 (or what your form says).
- Type width 3.5. With "Keep aspect ratio" ticked, the height should come out at about 4.5.
- Save as JPG and tap Resize image.
The Image Resizer also has a ready "Photo 3.5×4.5 cm" preset, which fills in these values for you.
Method 2: Passport photos in one step
If you need a passport-style photo of 3.5 × 4.5 cm (35 × 45 mm), the Passport Photo Maker is quicker. Choose "India passport / visa (35 × 45 mm)", zoom and drag your face into the guide, and download a single photo or a 4×6 print sheet. It also has presets for 2 × 2 inch, PAN card (25 × 35 mm) and stamp size. For more on the size itself, read our guide to passport size photo size in India.
Why not just type 3.5 × 4.5 cm into a resizer?
You can, but if your photo isn't already in a 7 : 9 shape, one of two bad things happens:
- With "Keep aspect ratio" on, the height won't be 4.5 cm. You'll get, say, 3.5 × 4.7 cm.
- With it off, the photo is stretched and your face looks too wide or too thin.
Cropping first avoids both problems. That's why we always crop, then resize.
Crop image in cm on mobile
Both tools work in phone browsers. On a phone, drag the crop box with one finger and drag the orange corner handles to make it bigger or smaller. Typing the width and height in pixels is often easier than dragging precisely on a small screen. Files download to your Downloads folder (Android) or the Files app (iPhone).
Crop to exact size and reduce KB
Online forms often ask for a size in cm or pixels and also a limit in KB. After cropping and resizing, run the photo through the Image Compressor with the KB limit. For exam forms that list exact pixels and a KB range together, the Exam Photo & Signature Resizer does crop, resize and KB in one step.
Printing at the exact size
- Print at 100% or actual size, never "fit to page".
- Make sure the DPI you used matches the print. A 413 × 531 px photo prints at 3.5 × 4.5 cm only at 300 DPI.
- Measure the printed photo with a ruler to confirm.
Frequently asked questions
How many pixels is 3.5 × 4.5 cm?
At 300 DPI it is 413 × 531 pixels. At 200 DPI it is 276 × 354 pixels.
How do I crop a photo to 3.5 × 4.5 cm online?
Crop it to a 7 : 9 shape (for example 700 × 900 px) in Crop Image, then resize it to 3.5 cm wide at 300 DPI in the Image Resizer.
Does cropping reduce quality?
No. Cropping keeps the original pixels inside the box. Resizing down and saving as JPG cause only a small, usually invisible, change.
Can I crop an image in inches or mm?
Crop by shape in pixels, then resize using the Millimetres or Inches unit in the Image Resizer.