What size should a wedding invitation be in design software?

Short answer

Set your design canvas to the finished size of your card, usually A6 (105 x 148 mm) or A5 (148 x 210 mm). Always add a 3 mm bleed around the edges so colours and patterns print right to the edge without white lines.

Start by choosing the card size you want to send. The most common sizes are A6, which is a compact postcard style, and A5, which folds or feels more generous. In your design software, create a new document at the exact finished size, then add a 3 mm bleed on all four sides. That bleed area is extra space for your background colour or design to extend beyond the cut line, so when the card is trimmed there is no white border.

Work in CMYK colour mode rather than RGB, because that matches what printers use and keeps your colours looking true on paper. Set your resolution to 300 dots per inch so text and images stay sharp. If you are printing at home, you can still use the same setup; just remember that home printers often cannot print right to the edge, so you may need to leave a white border or trim the card yourself.

Keep your main text well inside the safe area, about 5 mm from the edge, to avoid anything being cut off. If you plan to use a matching envelope, check the envelope size before you finalise your card size, so the invitation slips in without folding or scrunching.