The most common business envelope sizes include:

  • #10 Envelope (4.125″ x 9.5″) – Standard business correspondence and invoices
  • A7 Envelope (5.25″ x 7.25″) – Invitations and greeting cards
  • 9″ x 12″ Envelope – Documents that should not be folded
  • 10″ x 13″ Envelope – Large documents, catalogs, and reports

The right size depends on what you’re mailing and how professional you want the presentation to appear.