Wedding Invitation Postage Calculator

How invitation postage actually gets calculated

Postage is a function of three things: weight, envelope shape, and whether the envelope can go through the sorting machinery. The Wedding Invitation Postage Calculator works in all three at once, for both USPS and Canada Post, because a surprising number of couples in border states and provinces have guests on both sides.

You enter how many invitations you are mailing, which country or countries you are mailing to, your envelope size, and what is going inside. The tool adds the pieces by weight in grams, decides whether the finished envelope is machinable, applies the correct rate band, and returns a per-envelope cost and a total, with RSVP return postage accounted for separately.

Why your square envelope costs more

USPS processing machinery sorts rectangular mail by its long edge. A square envelope cannot be oriented the way the machine expects, so it has to be handled by hand, and the post office charges a non-machinable surcharge on top of the normal rate. The same principle applies to any envelope that is too rigid, too thick or too irregular to bend through the sorter.

Wax seals are the other common trigger. A single thin seal often passes. A seal that pushes the finished envelope over roughly fifty grams, or a thick seal with a vellum wrap beneath it, generally does not, and the tool treats it as non-machinable. The practical consequence is a higher per-envelope price and a longer delivery time, not a refusal.

What the enclosures actually weigh

Invitation cards run around 28 grams for an A7 and around 35 for an A9, with square cards in the same range as the A9. The outer envelope adds roughly 10 grams, an RSVP card 8, and an RSVP envelope 7. A details or accommodations card is around 8 grams, a map or directions card around 5, and a menu card around 5. An inner envelope adds 8, a vellum wrap 5, and a wax seal 7.

USPS rate bands turn at one ounce, which is 28.35 grams, and again at two ounces, with a per-ounce charge beyond that. Canada Post bands turn at 30, 50 and 100 grams. Because the bands are wide, small additions often cost nothing at all, and one card can push you from one band to the next. That is why the calculator is worth running before you buy stamps rather than after.

Non-machinable envelopes need one trip to the counter

If the tool flags your invitation as non-machinable, its advice is specific: assemble one complete invitation exactly as a guest will receive it and take it to the post office to be weighed at the counter before buying anything in bulk. A counter weighing is definitive, the online calculators are estimates, and stamps bought in the wrong denomination are not refundable.

Once you know the correct denomination, buy roughly ten percent more stamps than you have invitations. Assembling is where mistakes happen, addresses get spoiled, guests get added late, and a handful of spare stamps costs far less than a second trip to buy more of a specific denomination.

RSVP return postage is a separate line

Every RSVP envelope you enclose is an extra stamp on top of the invitation itself, and it is the item couples forget when they budget. The calculator adds it as its own figure rather than folding it into the per-envelope cost, so you can see the two side by side: the invitation going out and the reply coming back.

Enclosing a stamped, pre-addressed RSVP envelope is the single change that most improves response rates, which is why it remains standard practice even though every reply costs you a stamp. If you need to economise, the place to do it is the enclosure stack rather than the return stamp.

Mailing across the border

If you are posting to guests in both the United States and Canada, run the calculator for each country rather than averaging. The rate structures differ in shape as well as in price: USPS bands turn on ounces at 28.35 grams and again at two ounces, while Canada Post bands turn at 30, 50 and 100 grams. An invitation that sits in one band on one side of the border can sit in another band on the other, and mixing the two into a single stamp purchase is how people end up short.

Buy the stamps in two batches and post them separately. Mixed cross-border stacks get sorted by hand and delayed.

Decorative stamps and the denominations problem

Vintage and decorative stamps are often issued in denominations that do not match the exact postage on a heavy or non-machinable envelope. That is not a problem, but it changes the shopping. The post office can pair a decorative stamp with a low-value make-up stamp to reach the correct total, and buying the make-up values at the same time as the decorative ones saves a second trip.

In Canada, postage can be printed at home through the postal service's own online tool, which sidesteps denominations entirely and produces a label rather than a stamp. For a large mailing that can be the difference between weighing a hundred envelopes and weighing one.

Frequently asked questions

How much does it cost to mail 100 wedding invitations?

At a standard one-ounce USPS rate, about $73 for the invitations themselves, plus roughly the same again if you are enclosing a stamped RSVP envelope, plus any non-machinable surcharge and the cost of a few spare stamps.

Why are square wedding invitations more expensive to mail?

Because the sorting machinery orients mail by its long edge, and a square envelope cannot be squared up to the machine the way it expects, so it has to be processed by hand and carries a non-machinable surcharge.

Do wax seals need extra postage?

Often, yes. A thin single seal frequently passes as machinable, but once the finished envelope is heavy or the seal is thick, it is treated as non-machinable. Assemble one and have it weighed at the counter rather than guessing.

Should I weigh one invitation or just estimate?

Weigh one, fully assembled, at the post office. The enclosure weights the tool uses are accurate averages, but paper stocks vary, and a heavier card stock can move you into the next band on its own.

How many extra stamps should I buy?

About ten percent more than your invitation count. That covers spoiled addresses, late additions and assembling mistakes without a second trip for one specific denomination.

Does an inner envelope change the postage?

It adds weight, roughly 8 grams, and it can also make the stack thick enough to be treated as non-machinable. Both effects are reflected in the calculation when you select the option.

Related planning tools

Set the mailing dates with the Save the Date & Invitation Timeline and track replies with the RSVP Deadline Calculator. Get the wording right with the Invitation Wording Formula, plan the stationery spend with the Budget Category Breakdown, and keep the overall number honest with the Total Wedding Budget Calculator.