Once you have calculated how many wedding invitations you need to order based on your guest list, be sure to order a few extras to allow for any last-minute guests and to save at least one for your wedding album. It's usually cheaper to include extras in your original order than to place an order for a small quantity later. In some cases, you might be able to also order a few extra envelopes to accommodate addressing errors or undeliverable/returned invitations that need to be re-mailed.