The three things to check
- Dimensions are the width and height in pixels, for example 1,200 × 800. They describe how many pixels the picture contains, not how big it looks on a screen.
- File size is how much storage the file uses, in KB or MB. A 4,000-pixel phone photo is often several MB.
- Format is the file type: JPG, PNG, WebP, GIF and so on. Forms often accept only some of them.
Dimensions and file size are related but not the same. A big image can have a small file size if it is simple or heavily compressed, and a small image can be large if it holds fine detail. The relationship is covered in file size vs dimensions.
Check against a form's limits in your browser
The quickest route when a form states limits is Upload Check:
- Add your images. The workspace takes up to 20 files at 20 MB each.
- Choose a preset or enter your own limits: the accepted format, maximum file size and maximum dimensions.
- Read the report. Each image shows its format, size and dimensions and whether it passes or fails.
- If something fails, process the images and check the outputs again before downloading.
The check works on files in your browser, so nothing is uploaded to run it. Note what it does and does not do: it compares the limits you entered, using maximum dimensions rather than exact ones, and it cannot check things like face position, background colour or the website's other rules. A pass does not guarantee the other site will accept the file.
On Windows
Right-click the file and choose Properties. The General tab shows the size (look at "Size", not "Size on disk"), and the Details tab shows image dimensions, plus bit depth and other data. In File Explorer you can also add Dimensions and Size as columns in Details view. The file type appears in the "Type of file" line on the General tab.
On Mac
Select the file and press Command-I for Get Info. It shows kind, size and, under More Info, the dimensions. Opening the image in Preview and choosing Tools, then Show Inspector gives the same pixel dimensions. Note that Mac reports sizes in decimal units (1 KB = 1,000 bytes), whereas Windows has often shown binary-style figures, so the same file can read slightly differently on two computers.
On iPhone and Android
- iPhone: in Photos, open the picture and swipe up (or tap the info button) to see the file name and details; newer versions of iOS also show dimensions and file size there. In the Files app, long-press the file and choose Get Info for size, type and dimensions.
- Android: open the photo in Google Photos or your gallery, tap the three-dot menu or swipe up for Details, which lists name, resolution and size. In the Files app, open the file's details panel.
Exact menu wording varies by phone model and software version, so if you do not see these options, look for an "i" icon or "Details".
KB vs MB, and why numbers differ
WORDMIO uses decimal units: 1 KB is 1,000 bytes and 1 MB is 1,000,000 bytes. Some systems use binary counting, where 1 KB is 1,024 bytes. On a 200 KB limit the difference is 4,800 bytes: 200 KB is 200,000 bytes in decimal and 204,800 bytes in binary. So a file reading 198 KB on one system may read 193 KB on another. Always leave about 10 percent of headroom under a limit. The topic is explained in what does 100 KB mean.
Fix what fails
| Problem | Fix |
|---|---|
| File too big (KB or MB) | Compress image with a target slightly under the limit, or reduce pixels first |
| Dimensions too large | Resize image, which fits the picture inside your width and height without stretching |
| Wrong shape | Crop image to the ratio needed, then resize |
| Wrong format | Convert to JPG, PNG or WebP |
Work on a copy, and when two limits are both too high, resize first and compress second, since fewer pixels leaves more room for quality. Resize only reduces dimensions and does not enlarge smaller images, so it will not fix an image that is too small.
Common mistakes
- Judging by how large the picture appears on screen instead of its pixel dimensions.
- Renaming .png to .jpg. The data is unchanged, so the form may still refuse it.
- Reading "Size on disk" in Windows, which is the storage allocated, not the file size.
- Compressing the same JPG repeatedly. Start again from the original each time.
- Forgetting the form's other rules, such as minimum size, background or exact dimensions. For more, see the image upload guide and online application image requirements.
Frequently asked questions
How do I check the dimensions of an image?
On Windows right-click the file, choose Properties and open the Details tab. On Mac use Get Info or Preview's Inspector. In a browser, Upload Check shows width and height.
How can I see an image's file size?
Right-click and choose Properties on Windows, press Command-I on Mac, or open the Details panel in your phone's gallery or Files app. WORDMIO's Upload Check shows it too.
Are pixels the same as KB?
No. Pixels measure the picture's width and height, while KB measures storage. A larger image usually has a larger file, but format and detail change that.
How do I know if my image meets an upload form's limits?
Enter the form's format, maximum size and maximum dimensions into Upload Check and add your image. It reports what passes and what needs fixing.
Put it into practice.
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