Start with the insert
Measure the card, note, photo, or cash gift. Add at least 0.25 inches of clearance to the width and height so the insert slides in without catching.
Common sizes
A 4.25 by 5.5 inch card needs an envelope around 4.5 by 5.75 inches. A cash gift fits well in a 3.25 by 7.25 inch envelope. Mini notes can use 2.5 by 3.5 inches.
Paper choice
Text weight paper folds neatly for everyday envelopes. Lightweight cardstock works for gift-card envelopes, but score every fold before gluing.
Glue tabs
Keep side tabs narrow, around 0.35 to 0.5 inches. Wider tabs waste interior space and can make the envelope bulky.