How can you tell how many mb a photo has?

To determine the size of a photo in megabytes (MB), right-click on the image file and select "Properties" on Windows or "Get Info" on macOS. The file size will be displayed in the properties window, usually in bytes, kilobytes (KB), or megabytes (MB). If it's in bytes or KB, you can convert it to MB by dividing by 1,024 for KB or 1,048,576 for bytes. Alternatively, you can view the file size directly in file management applications or photo editing software.