This value will likely be measured in megabytes (MB).
Windows - Double-click “My Computer”, then double-click the iOS device in the “Devices and Drives” section. Mac - Double-click the iOS device icon that appears on your desktop.
Windows - Right-click on the image, then click Properties. Mac - Select the image, hold down Command, and tap I.
The photo’s size should be next to a heading that says “Size” or “File Size. "
If you didn’t add a subject to your email, you’ll have to confirm that you want to send the email without a subject before continuing.
If you selected multiple photos, you’ll only see their total size (not a photo-by-photo breakdown).