In short: Turn on airplane mode, then send the picture as an attachment. It brings up a dialog with the file size. Then delete the message from your outbox.
The iPhone lets you do a lot of different things with photos, but it doesn’t let you see the file size of your photos. Here’s how to do it.
- Turn off all data (Airplane mode on and wifi off). This makes sure you don’t actually send an email.
- Pick the photo you want to see the size of and send it as an email.
- Pick a random email address and then click Send.
- Before it is done, it’ll bring up a dialog that asks you to choose the file size of the image. The size of the file will be shown as the bottom button.
- Choose one of the options and delete the message from your Outbox. I don’t believe this works for smaller images, but if you’re trying to find the file size of a larger photo, this will tell you.