How to Fold a Letter for a Window Envelope

What You’ll Need

A standard #10 envelope (4 1/8 x 9 1/2 inches)
The letter or document to be mailed (standard 8.5 x 11 inches)
A flat, clean surface

Step-by-Step

Check the window position. Look at your envelope: the window is almost always on the front, left side, about 1 inch from the bottom. The recipient’s address should appear through this window when the letter is inserted.
Place the letter face up. Lay the letter on the flat surface with the side that contains the recipient’s address facing up. Make sure the address is at the top of the page, as it would be when reading.
Fold the bottom third up. Take the bottom edge of the letter and fold it upward so that it covers about two-thirds of the page. The crease should be at roughly the bottom third of the letter. The bottom of the page should now be near the middle of the letter.
Fold the top third down. Now take the top edge (where the address is) and fold it down over the first fold. The address should now be on the outside of the folded letter, facing you. The final folded size should be about 3.5 x 8.5 inches.
Insert the letter into the envelope. Hold the envelope with the window facing you. Slide the folded letter in with the address side facing the window. The top of the letter (the fold you just made) should go in first, so that the address is near the bottom of the envelope, aligned with the window.
Adjust and seal. Gently move the letter inside the envelope until the address is fully visible through the window. Once aligned, seal the envelope.

Common Mistakes

Folding the letter in half instead of in thirds – the address ends up too low or too high for the window.
Inserting the letter with the address side facing away from the window – the address is hidden.
Not aligning the address to the window – it may be partially cut off or shifted.
Using a letter that is too thick (like a folded brochure) – it may not fit through the window properly.

Tips

Use a bone folder or the edge of a ruler to make sharp creases – this keeps the letter flat and easier to insert.
If your envelope window has a plastic film, make sure the address is not too close to the edges of the paper – leave at least a 1/4 inch margin.
For a professional look, print the address in a standard font (like Arial or Times New Roman) at 10-12 point size.
If you’re mailing many letters, fold all of them the same way to save time.

Troubleshooting

Address not showing at all: Remove the letter and check the orientation. The address side must face the window. If it’s still not visible, re-fold with the address on the outside of the final fold.
Address is partially cut off: Slide the letter up or down inside the envelope. If it’s too low, push it up slightly; if too high, push it down. Ensure the address is centered in the window.
Letter is too big for the envelope: If the letter is thicker than a few pages, it may not fold flat. Try using a larger envelope or reduce the number of pages.
Window is on the right side: Some envelopes have the window on the right. In that case, fold the letter so the address is on the right side when inserted. Adjust the orientation accordingly.

Frequently Asked Questions

What is the standard fold for a letter?

The standard is a tri-fold: fold the bottom third up, then the top third down. This fits a #10 envelope.

Can I use a different size envelope?

Yes, but the folding method changes. For smaller envelopes, you may need to fold the letter in half or use a different pattern. Always test with a blank sheet first.

How do I know which side faces the window?

The side with the recipient’s address should face the window. If you’re unsure, insert the letter and check – the address should be readable through the plastic.

What if my letter has a logo or header at the top?

That’s fine. Just make sure the address is below the header and within the window area. You may need to adjust the fold position slightly.

Can I fold a letter with multiple pages?

Yes, but stack them neatly before folding. If the stack is too thick, consider using a larger envelope or a flat mailer.

Why does my address appear upside down?

You’ve inserted the letter with the top edge first. Turn the letter around so the bottom edge goes in first – the address will be right side up.

Sources: USPS. Menus and buttons can differ slightly by version. Spotted something out of date? Tell us.