@Lloltic Every card is a little different. That being said, if you have a card formatted in one format it will show a different amount of disk space in another.
It sounds like you have downloaded/backed up a pre-built image and are trying to burn it to a new card. The best thing you can do is burn it to the SD card and see if it will fit. Let the application tell you it won't, not your eyes. The other suggestion is to use PiShrink to shrink it down.
Keep in mind if it is a 3rdparty image you'll be hard-pressed to find support for it here if you do get it going.