What is an image file size?

Images are composed of several dots called pixels, and each of them has a color represented as a combination of three basic colors (red, green, and blue). To store each of these pixels, 3 bytes (24 ones or zeros) are generally used. When an image is large, it may have millions of pixels, which means storing all this information on a computer or any device takes up millions of bytes.

When a camera or cellphone says it takes 10 megapixels photos, it means that each photo has 10 million pixels (mega = million). And having 10 million pixels means it takes 30 million bytes (or 30 megabytes) to store that photo. If you want to send this photo (or many photos) to a friend by e-mail, it will require transferring 30 megabytes of data, which will take time to upload and download.

How to Reduce Image File Size Without Losing Quality

One way is by compressing the image, which reduces file size without resizing it. However, increasing compression may cause some quality loss as data is removed.

Another method is resizing your photo, reducing the pixel dimensions of the image. Resizing does not reduce image quality, although small details may be lost.

Most photos from modern cameras and cellphones have over 6 million pixels, but most screens only display around 1.5 million pixels. This means you often view a resized version of the image unless printing it. By reducing the image's width and height, the number of pixels matches the screens displaying it, retaining quality even in full-screen mode.

If you have a large photo, resizing it to around 1900 by 1100 pixels in JPG format with 90% quality will give you a high-quality, versatile image that is quick to share.