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What Size Envelopes Require Additional Postage?

What Size Envelopes Require Additional Postage?


The size of the envelope that you use to send a letter or other item using the United States Postal Service (USPS) is definitely going to affect the amount of postage you will need to pay to get it to your intended destination. So what size envelopes require additional postage? We will answer this question and others in this article.

The letter sized envelope mail class is the First Class mail service. There are other ways that you can send letters such as the Priority Mail or Priority Mail Express services. The more expensive priority services are there to provide faster delivery of your item so you need to decide which is best for your requirements.

What is the Eligibility Criteria for mailing at the standard Letter Rate?

If you want to pay the lowest price for mailing something then you need to use a rectangular envelope. The envelope needs to be a minimum of 3.5 inches in height by 5 inches in length and the thickness must be a minimum of 0.007 inches.

To be eligible for the standard letter rate and envelope cannot be more than 6.125 inches in height by 11.5 inches in length and have a thickness greater than 0.25 inches. Anything that exceeds these dimensions will incur additional postage.

So if your question is “how big of an envelope can I send with one stamp” then the answer is 6.125 inches in height by 11.5 inches in length and a thickness no greater than 0.25 inches. This also answers the question “what is the largest envelope for a regular stamp?”

Other Factors to take into Account

If the item that you are sending has some non machinable characteristics then you will have to pay a surcharge to send them above the standard letter postage rate. This is often a shock to people that are expecting to pay the standard postage rate.

One classic example of this is the sending of square greeting cards. Because they don’t use a rectangular shape envelope it is not easy for the postal machines to process and therefore an additional charge will apply.

In fact if you use any kind of differently shaped envelope such as a square or a rigid type of envelope then these can actually jam up the postal machines and they have to go through a different mailing process which involves human interaction.

When the standard mailing process doesn’t apply it means that there are extra costs for the USPS and you as the customer bear the brunt of these costs. So it is in your interest to check that your envelope is not an odd shape or that it will not go through the automatic postal machines because of its constitution.

If you insist on using different shape envelopes or those made from rigid materials not only will you end up paying more for the postage but you also run the risk of your item suffering damage as it makes its way through the system.

Large Envelope Postage

The USPS will often refer to large envelope sizes used for the First Class mail service as “flat mail”. Basically a large envelop is one that exceeds the maximum size of 6.125 inches in height or 11.5 inches in width or has a thickness greater than 0.25 inches.

So why would you want to pay large envelop postage when you can use an envelope that meets the requirements for the lowest level of postage cost? Well there are a number of reasons for this.

You may want to send a book or a manuscript that will exceed the maximum envelope thickness requirements. Other items that will force the thickness of the envelope to be grater are items such as CD’s or DVD’s, reports, magazines and large documents which you do not want to fold in any way.

Some legal documents require a larger envelope size as do some brochures and other marketing materials. Product catalogs are certainly going to require a larger envelope for example.

When you need to use a larger envelope you need to understand that there are maximum dimensions to take into consideration as well. To pass as flat mail an envelope cannot be more than 0.75 inches thick. You cannot use an envelope that is more than 12 inches high for flat mail or greater than 15 inches in length.

No matter what size of envelope you use for your item the weight of your package (including the envelope) must not exceed 13 ounces. If you exceed any of the above dimensions then you will have to pay parcel rates rather than letter rates which are more expensive.

So how much more will you need to pay for using an envelope that exceeds the maximum standard rate postage charge? Well the price will start at $1 and will rise by 15 cents for every additional ounce that your shipment weighs.

Do you need to visit the post office every time you need to use a larger envelope and pay large envelope postage? Well not unless you have a postage meter or you have the ability to print your postage online using the services of a company that offer this arrangement. Other than that you will need to make a trip to the post office to know what the cost will be.

If you are going to use a large envelope to send your item then don’t take the risk of using standard letter postage rates if you have some stamps available. Measure your envelope properly and weigh it.

When you send an item through the postal system with insufficient postage it will create delays. The USPS will not send your item until you have paid the correct amount. You cannot buck the system and it is not even worth trying to do this. Why go through all that hassle for the sake of a few extra cents? It really isn’t worth it.

What Size Envelopes Require Additional Postage

Letter Sized Envelope Postage and 5 x 7 Envelopes

A question that a lot of people ask is “do 5 x 7 envelopes require extra postage?” The answer to this is “no” as long as the items within the envelope do not exceed the maximum weight restrictions.

There are several reasons why you might want to use a 5 x 7 envelope. Many invitation and RSVP cards fit nicely into an envelope of this size. They are also convenient for sending hand written letters.

The good news here is that the 5 x 7 inch envelope is the standard size accepted by the USPS for sending invitation cards and letters. So as long as the contents of the envelope does not exceed one ounce you will pay the normal standard letter rate and there will be no additional charges.

If you do exceed the weight limit then you will have to pay an additional charge. Sometimes it is necessary for you to send more than just a single invitation card (such as an RSVP card and a reception card as well). If you use folded or layered invitations then this will very likely result in additional charges as well.

Be careful to avoid 5 x 7 envelopes where the thickness including the contents will exceed 0.25 inches. Letters that exceed this thickness will have problems when it comes to the machines that the USPS uses for the sorting and distribution of mail. If it is not possible to use standard machines then their costs rise and so will yours.

Avoid using rigid envelopes as well and don’t use a square envelope unless you have to. These will definitely cause problems for the USPS machines and you can expect to pay a minimum of 21 cents extra per mailing in this situation.

If a standard USPS machine cannot process an envelope then they will require manual stamping and processing which takes more time. There is also the cost of the worker to factor to consider as well. Non machinable envelopes are also more likely to suffer damage while they are in transit as well so think very carefully before you choose these options.

If you are not certain whether a particular sized or shaped envelope will attract the standard charge then the best thing to do is to visit the post office and get it checked out. You will need to add the contents to the envelope as well to check the correct weight.

Envelope Size Postage Rates

If you are using an envelope size that conforms with the dimensions laid down by the USPS for letter rate then at the time of writing the minimum cost for the First Class mail service is 55 cents.

If your envelope exceeds the dimensions for the standard rate then prices start from 70 cents and go up dependent on the total size and weight. The same starting rate of 70 cents applies if your envelope is square or has some other kind of unusual shape.

Some people like to send postcards and for a standard size postcard the First Class mail service starts at 35 cents. If your postcard is larger than the standard size you will have to pay the same as the letter rate which starts from 55 cents.

So we have answered the question “what size envelopes require additional postage?” in this article. We have answered other questions as well such as “how big an envelope can I send with one stamp?”, “what is the largest envelope for a regular stamp?” and “do 5 x 7 envelopes require extra postage?”

If you stick within the dimension and envelope type limits specified by the USPS then you are unlikely to pay more. Don’t go for square envelopes or those with unusual shapes if you can avoid it. If in doubt go to your post office and ask.