What is the Legal Size Envelope?

The size of an envelope is important to know when sending a letter or other type of document through the mail. The standard size for a letter is a #10 envelope, which measures 4 1/8 inches by 9 1/2 inches.

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The #10 envelope is the most common size used for business correspondence. The dimensions of a #10 envelope are 4-1/8 inches by 9-1/2 inches. This size envelope can be used for standard 8-1/2-inch by 11-inch documents that have been folded in thirds.

The Different Types of Legal Size Envelopes

There are a few different types of legal size envelopes, and each has its own purpose. The standard legal size envelope is the #10 envelope, which is typically used for official documents or letters. The #9 envelope is a bit smaller and is often used for personal correspondence. The #11 envelope is the largest legal size envelope and is usually used for shipping documents or large letters.

Standard #10 Envelope

The standard #10 business envelope is the most common type of envelope used for sending letters through the mail. It measures 4-1/8″ x 9-1/2″, making it just slightly larger than a sheet of standard 8-1/2″ x 11″ paper. The #10 envelope can be used for documents that are up to 3/4″ thick when unfolded, making it a good choice for sending thicker documents or multiple pages at once.

Flat Rate Envelope

The USPS offers a variety of envelope sizes for different types of mail. The most common size is the #10 envelope, which is used for standard business correspondence. The next most common size is the 6″ x 9″ envelope, which is typically used for marketing materials such as brochures and catalogs.

There are two types of 6″ x 9″ envelopes – the regular (or “flat”) envelope and the padded envelope. The regular 6″ x 9″ envelope can accommodate up to 5/8″ thickness of paper, while the padded envelope can accommodate up to 1″ thickness of paper.

The next largest size is the 9″ x 12″ envelope, which is commonly used for legal documents and larger marketing materials. Like the 6″ x 9″, there are both regular and padded versions available. The regular 9″ x 12″ envelope can accommodate up to 3/4″ thickness of paper, while the padded envelope can accommodate up to 1 1/2″ thickness of paper.

For very large items, such as posters and blueprints, you may need to use a flat rate box instead of an envelope. The USPS offers several different flat rate box sizes, ranging from small (8 11/16″ x 5 7/16″) to extra large (24 11/16″ x 11 3/4″).

Window Envelope

A window envelope has a die cut window in the frontpanel that allows the recipient address to show through. Thewindow is generally lined with a thin film of clear plastic (polyurethane)to keep the bonding together and prevent moisture or other contaminantsfrom damaging or soiling the contents.

Different manufacturers will have different standard sizes for theirwindow envelopes, but the most common size is the #10 businessenvelope which measures 4-1/8 inches by 9-1/2 inches. Other popular sizesinclude the #9 (3-7/8 inches by 8-7/8 inches), #11 (4-1/2 inches by 10-3/16inches), and #14 (4-3/4 inches by 11-1/4 inches) envelopes.

Double Window Envelope

A double window envelope has two windows, allowing the recipient and return addresses to be visible. This type of envelope is commonly used for bills, invoices, and other types of correspondence where both the mailing and return addresses need to be visible.

How to Choose the Right Legal Size Envelope

There are two common types of envelopes: letter and legal. Legal envelopes are slightly larger than letter envelopes and have a flap that sticks out. This type of envelope is typically used for sending important documents, such as legal papers or tax documents. If you’re unsure which envelope to choose, it’s best to consult with a professional.

Consider the Contents of the Envelope

Before you can choose the right legal size envelope, you need to consider the contents of the envelope. If you are sending standard paperwork, such as a letter or contract, then a standard 9” by 12” envelope will be sufficient. If you are sending larger items, such as a booklet or a poster, then you will need a larger envelope, such as a 10” by 13” envelope. Additionally, if you are sending multiple items in one envelope, such as several photos or sheets of paper, then you will need to choose an envelope that is large enough to accommodate all of the items.

Determine the Appropriate Closure

Before you choose your legal size envelope, you need to determine the appropriate closure. The most common envelope closures are gummed, self-sealing and peel & stick.
-Gummed: these envelopes require moistening the adhesive strip before sealing.
-Self-sealing: these envelopes have a strip of adhesive that activates when pressure is applied during sealing.
-Peel & stick: these envelopes have an adhesive strip that does not require moistening before sealing.

Once you’ve determined the appropriate closure, you can choose your legal size envelope. Some common legal sizes include #10 (4-1/8″ x 9-1/2″), #9 (3-7/8″ x 8-7/8″) and #14 (4-3/4″ x 11-1/2″). Remember, you can always order custom sizes to fit your specific needs.

Select the Right Material

Paper quality is important when choosing a legal size envelope because you want your mailpiece to look professional. For example, if you are sending documents that need to be filed, you may want to choose a heavier paper so the recipient can reuse the envelope. If you plan on using your envelopes for mass mailings, you will want to choose a lighter paper so the postage is less expensive.

There are three basic types of paper used to make envelopes: wove, laid and text. Wove paper is smooth and available in a wide range of weights and colors. Laid paper has a linen finish and is available in weights ranging from 20 lb. to 60 lb. Text paper has a slightly rough surface and is available in weights ranging from 60 lb. to 100 lb


In conclusion, the legal size envelope is a great way to keep your documents safe and secure. It is also a great way to make sure that you are able to keep your documents organized.