Resize a picture using Paint
You can change the size or resolution of a digital picture by changing:
1) The number of pixels. The resolution, or sharpness, of a picture is determined by the number of pixels it has. More pixels improve the resolution of a picture, which allows you to make a larger print without reducing visual quality. Keep in mind, however, that the more pixels a picture has, the larger its file size will be.
2) The file size. The amount of space a picture takes up on your computer and how long it takes to send as an e‑mail attachment is determined by the picture's file size. Although more pixels often means a larger file size, the picture's file type (JPEG or TIFF, for example) usually has more to do with file size. For example, a picture saved using TIFF will be much larger than the same picture saved using JPEG. This is because JPEG pictures can be compressed, which makes the file smaller at the cost of slightly lower visual quality.
If the picture isn't already a JPEG, you can usually save a significant amount of space by saving the file as a JPEG, and then deleting the original TIFF version from your computer. For information about saving a picture as a different type of picture file using Paint, see Change a picture's file type (file format) using Paint.
Watch this video to learn how to resize a picture using Paint (1:26)
To resize a picture using Paint