Envelope Size Guide: Which Envelope Fits Your Paper?
Envelopes are named for the paper they hold, not for their own size. Learn the C-series pairings once, and you will never fold a letter into the wrong envelope again.
What is the Envelope Size Guide?
Choose an envelope size and the tool gives its dimensions and the paper it fits. The rule of thumb is simple: C4 fits A4 flat, C5 fits A4 folded once, C6 fits A5, and DL fits A4 folded into thirds.
How to use it
- Choose an envelope size.
- Click Show Envelope Size.
- Read its dimensions and the paper it fits.
Worked example
A C5 envelope measures 162 by 229 millimetres and fits an A4 sheet folded once.
What does the C in C5 mean?
C-series envelopes are sized to hold A-series paper: C4 holds A4 flat, C5 holds A4 folded once, and so on.
Frequently asked questions
What is a DL envelope?
A long, narrow envelope, 110 by 220 millimetres, made for an A4 sheet folded into thirds — the classic business-letter envelope.
Can I post a C4 envelope normally?
Yes, but check your postal service's large-letter limits, since C4 is bigger than a standard letter.