How to Check Image Dimensions and File Size Online (Instantly)
Before resizing, compressing, cropping, or uploading an image anywhere, it helps to know what you're working with. Here's how to instantly check an image's pixel dimensions, file size, aspect ratio, and megapixel count - all from your browser.
What Information Do You Need Before Editing an Image?
Knowing your starting point saves time and prevents mistakes:
- Pixel dimensions (width × height) - tells you if the image is large enough for a target size, and how much you can crop without losing resolution
- File size in KB or MB - tells you how much compression is needed to meet an upload limit
- Aspect ratio - tells you the proportional relationship between width and height (e.g. 16:9, 4:3, 1:1) which matters for cropping without distortion
- Megapixel count - a quick indicator of overall image resolution (width × height ÷ 1,000,000)
How to Check Image Size Online
LovePDFImg's Image Size Checker reads all this information from any JPG, PNG, or WebP image and displays it instantly - no upload to a server, no signup, and it handles multiple images at once for easy comparison.
Shows pixel dimensions, file size, aspect ratio, and megapixels. Add multiple images to compare.
- Open Image Size Checker on LovePDFImg.
- Upload one or more images - drag and drop or click to browse.
- Each image's details appear immediately:
- Pixel width × height
- File size (KB or MB)
- Simplified aspect ratio (e.g. 16:9)
- Megapixel count
- Add more images to compare sizes side by side.
How to Check Image Size on Your Device (Without a Tool)
Your device can also show basic image information:
- Windows: Right-click the image → Properties → Details tab - shows dimensions and file size
- Mac: Select the file in Finder → press Cmd+I for Get Info - shows dimensions and size. Or open in Preview → Tools → Show Inspector
- iPhone: Open in Photos → swipe up → see dimensions in the Details section
- Android: Open in Gallery or Photos → tap Info or Details icon
For quick checks, these built-in options work fine. For batch checking multiple images, or when you want to see the simplified aspect ratio and megapixel count alongside dimensions, the Image Size Checker is more efficient.
Practical Examples: Using Size Information
Scenario 1: Uploading a profile photo
The platform requires a minimum 400×400px image. Check the size of your photo first. If it's 800×600px, it meets the minimum - just crop it to a square and you're done. If it's only 200×200px, you'd need a different photo since upscaling would look blurry.
Scenario 2: Reducing for email
Your image is 4.2MB - too large to attach. Check the dimensions: 5000×3333px. That's enormous for an email. Resize to 1200×800px and the file will be roughly 400KB - then compress it to 150KB if still needed.
Scenario 3: Print preparation
A print service needs a 4×6 inch image at 300 DPI - that means 1200×1800 pixels. Check your image: it's 2400×1600px. You have enough pixels for width, but the ratio is different - crop to the right ratio first, then check again.
Related Tools for After You've Checked
Once you know what your image needs, the next step is usually one of these:
- Resize Image - change pixel dimensions to meet a requirement
- Compress JPG - reduce file size to meet an upload limit
- Crop Image - change aspect ratio or composition
- Change DPI - update DPI metadata for print requirements
- Aspect Ratio Calculator - calculate proportional dimensions for resizing
Key Takeaways
- Use Image Size Checker to see pixel dimensions, file size, aspect ratio, and megapixels - instantly.
- Add multiple images to compare sizes side by side.
- Use this information to decide whether to resize, compress, or crop.
- For print, also check if you have enough pixels for the required DPI with Change DPI guidance.
- Use Aspect Ratio Calculator to plan proportional resizing before changing dimensions.