A practical image guide

How to check image size: pixels, KB and MB

By Image Size Checker · Updated September 19, 2026

To check an image’s size, read two things: its width and height in pixels, and its file size in bytes, KB or MB. A file can pass one requirement and fail the other.

Use the exact file you plan to upload or send. A screenshot, a messaging-app copy, or a new export can have different dimensions and a different file size.

Check an image on your device →

1. Check image size in your browser

Open the image size checker. Select Choose Image, drag in a file, or paste an image from your clipboard. Try sample image works without your own file.
Read Pixel dimensions. For example, 1200 × 630 px means 1,200 pixels across and 630 pixels down.
Read File Size. The smaller line includes the exact number of bytes and the equivalent KB and MB.
Use Copy Dimensions for the pixel values, or Copy Summary and Download .txt for a report.

The check runs locally in your browser. No image upload or account is needed. JPG, PNG, WebP and other image formats work when your browser can decode them. HEIC support varies; converting to JPG lets you check that converted copy, not the original HEIC file.

Image Size Checker showing a 1200 by 630 pixel sample PNG, with exact bytes and KB and MB values beside the original preview. — The dimensions tell you how wide and tall the image is. File Size shows how much storage it uses.

2. Know which measurement you need

Dimensions are measured in pixels

Width and height describe the image’s pixel grid. A 1200 × 630 image has 756,000 pixels, or about 0.76 megapixels. A 2400 × 1260 image has the same shape but four times as many pixels. Neither number tells you how many KB the file uses.

File size is measured in bytes

The format, image detail and compression affect the number of bytes. A photograph and a simple logo can have identical dimensions but very different file sizes. Lowering JPG or WebP quality may reduce bytes without changing width or height.

KB and MB can use different conventions. This checker’s readout uses 1 KB = 1,024 bytes and 1 MB = 1,048,576 bytes. For upload requirements you can instead choose 1 KB = 1,000 bytes and 1 MB = 1,000,000 bytes. Match the destination’s instructions; compare exact bytes near a limit.

Aspect ratio and DPI answer different questions

Aspect ratio describes the shape: 1200 × 630 simplifies to 40:21. DPI metadata concerns physical print sizing and is not a substitute for pixel dimensions. This checker does not read embedded DPI. For a print job, confirm physical dimensions and resolution with the printer.

3. Check on a computer or phone

Windows

Open File Explorer and locate the image. The Details view shows file size; the Details pane can show additional properties for the selected file. Available image properties depend on the format and installed support. If pixel dimensions are not shown, choose the file in the browser checker. See Microsoft’s File Explorer guide.

Mac

Open the image in Preview, then open its Info/Inspector window. Use the general image information to inspect the size and resolution. The labels depend on your macOS version. See Apple’s Preview instructions.

iPhone

Open the photo in Photos, then swipe up or tap the Info button. Available metadata includes file size and other image details. If you export or share a converted copy, check that copy again before submitting it. See Apple’s photo information guide.

Android

In Files by Google, find the image and use its More menu → File info. The properties shown can vary; use the browser checker when you need both dimensions and exact bytes in one view. See Google’s file information instructions.

Available photo details depend on your device, software and file format.

4. Check whether an image meets an upload limit

After selecting an image, open Check upload requirements. Enter the required width and height, choose exact or minimum dimensions, and set a maximum file size and format if needed. Leave unused rules blank.

Consider these illustrative files under a requirement of 1200 × 630 px, no more than 500 KB, with both PNG and WebP accepted:

File	Pixels	Size	Result
Original PNG	1200 × 630	706 KB	Too large
Example WebP copy	1200 × 630	180 KB	Fits these rules

These are example values, not a promised compression result. Open Resize & optimize, select an accepted output format, and adjust quality. Download checks uses the generated file’s actual dimensions, bytes and format. The original result remains separate.

For an exact dimension requirement, use Crop to fit to change the shape without stretching. The crop frame can be moved with dragging or arrow keys, and its size can be adjusted with the slider. Review the preview before saving.

5. When the numbers do not match

The dimensions match, but the upload fails. Check file size, format and any other destination rules. Passing the rules entered in this tool does not certify all requirements.
The file says “200 KB” but exceeds a 200 KB limit. A rounded label can hide extra bytes. Check the exact count and confirm whether the destination uses 1,000 or 1,024 bytes per KB.
The picture is smaller after downloading or sharing. Measure the delivered file. A preview, screenshot or messaging app may resize or re-encode it.
A website image looks small but has large pixel dimensions. Its displayed size can differ from the source file. Save the source image to check it; this tool does not scan webpage URLs.
The output loses animation, transparency or metadata. Canvas exports may flatten animation and remove metadata. JPG also removes transparency. Keep your original and choose the output format for the intended use.

Check your image and its upload requirements →