Q&A for How to Know How Many Stamps to Use

USPS classifies a 9" x 12" envelope as a "flat." At this writing, the postage rate for flats is $1.00 for the first ounce, and $0.21 for each additional ounce. So the postage required for an 8-ounce flat is $2.47.

Your suggestion is helpful. However, some people might find it more convenient to use Forever stamps (or the equivalent).

Yes. However, the Postal Service would prefer that you mail the parcel at a post office, because they are required to make general inquiries about the contents of the package (for safety reasons).

170 grams equal almost exactly six ounces, so you would need $1.55 in postage, which means four first-class stamps (or three stamps plus a 5-cent stamp).

Yes, you will have to get a customs label, which requires naming the contents of the letter/package, etc.

Too many to apply to one envelope. Take it to a post office, have them weigh it, and pay for the appropriate postage.

That would require two forever stamps (or the equivalent) because of the weight.

That may mean that the combined weight of the card and the envelope is so close to one ounce that you should have them weighed before deciding how much postage to apply.

In early 2023 the cost was 87 cents. (That's for any letter measuring less than 11½" by 6 1/8" and weighing less than two ounces.)

No, not if the mailpiece weighs less than one ounce. A letter does not require extra postage if it weighs less than an ounce and is not longer than 11½ inches and not taller than 6 1/8 inches.

Two, plus a ten cent stamp (as of December 2020). However, if you can't get a 10 cent stamp, you can use 3. Note it'll be overpaying, but it'll still work.

It's actually 1 Forever stamp per ounce, so if your envelope weighs one ounce or less, it'll need 1 stamp, if it weighs 2 ounces or less (but more than one ounce), it'll be 2 stamps, and so on.

Yes. They will calculate the postage required and subtract the total value of stamps already on the package (which will bring the postage owed to zero if you calculated it correctly). They will then apply 'live' tracking to your package and will mail it for you. (You cannot get the package back at this point, because the their system will consider the package as 'accepted' as soon as it creates that tracking label.)

Forever stamps are always worth the current 1st class 1 oz letter rate. Postage for any package can be paid with stamps as long as the total value of stamps applied is enough to cover the postage needed. However, packages of over 10 oz or 1/2 inch thick must be either brought to the post office retail counter, have online postage, or postage from an imprint machine (ie: Pitney Bowes). This is an aviation security policy that essentially creates a 'paper trail'.

In the USA, if it contains nothing rigid and is fairly uniformly flat, as of Januart 2020, $1.40.

You can go to postcalc.usps.com/Calculator/Index?country=10440 , enter your shipping info, and select the appropriate package/letter type for pricing options. Note: If you sending overseas to a military address like a base, ship, or embassy (city, state are something like "APO AE" or "FPO AP", for example), it is treated like stateside mail with a few restrictions. Visit postcalc.usps.com/MilitaryRestrictions and enter the destination zip code to find out the specifics for that area.

Typically, size and weight determine price. All envelopes must be flat. Envelopes that can’t fit through automated processing equipment costs more to send; this includes lumpy or rigid envelopes, and those that have clasps, string or buttons. Unusually-shaped square or vertical envelopes will also cost more to send.

As of December 2019, $0.70. I've found the USPS website calculator at postcalc.usps.com to be the most help if you are adamant about avoiding the post office in person.

There are a few variables that will determine the postage price, like its origin and destination, which level of service you use (Ground, Priority, First Class, etc.) and the size of your envelope. Visit the Postage Price Calculator at postcalc.usps.com to get the best estimate.

Yes the post office sells stamps, money orders, etc. They also provide USPS logo labels for free.

Use about 4 Forever stamps. However, you may want to take it to the post office to be mailed instead; although this is not required, you can be absolutely certain the stamps added are accurate.