Resize photos for online applications: pixels and file size

When you add a photo to an online application, you usually have to hit three targets at once: pixel dimensions, file size and file format. The short answer is to find those three values, plus any rule about editing, in the instructions first, then resize to the right pixels and only after that reduce the file size. Specs change, so this guide focuses on reading the instructions, not on memorizing numbers.

Five things to find in the photo instructions

Every organization words its photo rules differently, but most set some of the items below. Note them down before you touch the photo.

Item	How it’s often written	What to check
Pixel dimensions	“at least 600 pixels wide and 750 pixels tall”	Is it a minimum, a maximum, a range or one exact size? Which number is the width?
File size	“between 200 KB and 5 MB”	Is there a minimum as well as a maximum?
File format	“.jpeg or .jpg”	Do they accept HEIC (the iPhone default) or PNG?
Shape or print size	“3:2 aspect ratio”, or a size in mm or inches	Does your photo have the same shape?
Editing rules	“must not be altered in any way”	Does that include resizing? Is there an official way to get a compliant file?

If the instructions give a print size and a resolution instead of pixels, work out the pixels yourself: inches × dpi, or mm ÷ 25.4 × dpi (an inch is 25.4 mm, and dpi means dots per inch).

Also watch the units. ZEKILO Studio counts 1 KB as 1,024 bytes, the same way Windows File Explorer does. Forms rarely say how they count, so leave some headroom instead of landing exactly on the limit.

Real examples: UK and Canadian passport photos

GOV.UK’s “Get a passport photo” page (checked 2026-09-30) says you need a digital photo to apply for a passport online. Under the quality rules, the photo must be:

• clear and in focus, and “in colour”
• “unaltered by computer software”
• at least 600 pixels wide and 750 pixels tall
• at least 50KB and no more than 10MB

The same page says “Do not crop your photo - it will be done for you.” It also notes that a photo from a booth or shop is more likely to be approved than one taken on your own device.

Canada’s passport photo requirements (checked 2026-09-30) describe the digital photo you need only when renewing online. The file must be .jpeg or .jpg and have a 3:2 aspect ratio in portrait mode. It must be at least 1,800 pixels high by 1,200 pixels wide, no larger than 4,500 by 3,000 pixels, and between 200 KB and 5 MB. It must be taken in person by a commercial photographer, and it must not be altered in any way, including with photo-editing software, filters or AI tools.

These two pages teach three lessons:

• Minimums matter. Both set a minimum file size, so compressing too hard can get a photo turned down.
• Sizes are often ranges. You need to land inside the range, not on one exact size.
• Some forms forbid editing. For these, don’t resize or compress the file yourself. Get a compliant file from the booth, shop or photographer, or follow the method the office describes.

If a form, such as a job portal, lists only pixel and file-size limits and doesn’t restrict editing, you can match it yourself as described below.

When the shape doesn’t match, crop first

If your photo’s shape differs from the spec, resizing alone can’t hit both the width and the height. In Resize Image, “Keep aspect ratio” is on by default. You enter one side, and the other follows the original proportions: h = round(w × H ÷ W), where W×H is the original size. A 4000×3000 photo set to 1920px wide becomes 1920×1440.

Turning it off lets you set both sides, but the photo gets stretched or squashed, which distorts a face. Keep it on. Resize Image doesn’t crop, so if the shape is wrong, crop the photo to the required ratio in your photos app first.

Small photos need care, too. “Don’t enlarge beyond the original” is on by default, so if the target is bigger than the original, the photo keeps its size and you see a note. Turning it off enlarges the photo, but adds no new detail, so it may look blurry.

Pixels first, then file size

Fewer pixels usually means a smaller file, so set the pixels first. Resize Image saves JPGs at quality 90. Our 4000×3000, 4.0 MB test image came out at 199 KB when fitted to 1920px wide, and at 2000×1500 and 246 KB when shrunk to 50%. Measured in desktop Chrome; results vary by device and browser.

If the file is still over the limit, lower “Quality” in Compress Image. The JPG default is 75. The same 4000×3000 test image came to 429 KB at quality 75 and 167 KB at quality 60, measured the same way. Lower numbers tend to blur text and edges, so zoom in before you send it. For help picking a number, see Photo compression quality. If the form has a minimum file size, don’t drop below it.

Format and photo data are handled along the way:

• If the form accepts only JPG and your photo is HEIC, Resize Image saves the result as JPG. To turn a PNG into a JPG, use Image Converter.
• Both tools leave location (GPS) and other metadata out of the result, and apply your phone’s rotation info so the photo is saved upright. Colors are saved as sRGB.
• If the form wants the photo as a PDF, Image to PDF places it on A4 or Letter paper.

How to do it with ZEKILO Studio

1. Open Resize Image and drag and drop your photo or pick it with [Choose files]. Resizing starts right away at the default (50%).
2. Under “Resize by”, choose “Width & height”, leave “Keep aspect ratio” on, and enter the width the form asks for. The big number on the result card is the new resolution, so check that the height falls inside the allowed range.
3. Save with [Download]. If the file is still over the size limit, add the saved file to Compress Image, lower “Quality” and save again.

Your photos are processed in this browser and never leave your device. You can add up to 50 photos at a time, and files over 100 MB each are not processed.

Summary

• Find the pixel size, file size, format, shape and editing rules in the instructions before you start.
• If only a print size is given, convert it: inches × dpi, or mm ÷ 25.4 × dpi.
• If the form forbids editing, get a compliant file from the source it names instead of resizing it yourself.
• If the shape is different, crop first, then resize with “Keep aspect ratio” on.
• Set the pixels first, and lower the quality only if the file is still too big. Leave some headroom.