Images
What is Pixel?
A pixel is a single square of color in a digital image. An image’s pixel dimensions, such as 1200 × 800, say how many it contains.
How it works
Raster images are grids. Each cell in the grid is a pixel holding one color value, and sometimes a transparency value as well. Pixel dimensions tell you how many samples an image contains horizontally and vertically.
More pixels can represent more detail, but only if the source contains it. A photo taken with a good camera and a blurry photo resized to the same dimensions have the same number of pixels and very different amounts of detail.
Pixels vs file size vs DPI
Pixel dimensions set the potential detail. File size, in kilobytes or megabytes, depends on how those pixels are compressed: a flat graphic compresses well, a noisy photo doesn’t. DPI only says how large to print the pixels. Upload forms may limit any of the three, so read the requirement carefully: “at least 600 × 600 pixels” and “under 200 KB” call for different fixes.
A practical example
An image measuring 1200 × 800 pixels contains 960,000 pixels, just under one megapixel. Its file size also depends on format, content and compression.
What to watch out for
Pixel dimensions and file size aren’t the same thing. Two pictures with identical dimensions can have very different sizes in bytes, and enlarging a small image doesn’t add real detail.
Tools you can use
- Image Resizer · Scale to a size, a percentage or a platform preset
- Image Compressor · Cut file size with a visible quality trade-off
- Image Cropper · Drag a crop box or type exact coordinates
- Combine Images · Side by side, stacked or in a grid
Go a little deeper
- How to crop a photo to an exact size or ratio
- How to make an image 300 DPI
- How to put two photos side by side
- How to reduce image size without losing visible quality
Common questions
How many pixels do I need for a good print?
About 300 per inch of print for close viewing. A 6 × 4 inch photo needs roughly 1800 × 1200 pixels; a poster seen from a distance can use far fewer per inch.
What is a megapixel?
One million pixels. A 12-megapixel phone photo is about 4000 × 3000 pixels.
Why does my image look blurry when I make it bigger?
Enlarging has to invent new pixels between the existing ones. Software estimates them from their neighbors, which softens edges rather than recovering detail that was never captured.