How to Weigh Invitations Without a Postal Scale
You do not need a postal scale. A kitchen scale, a stack on a larger scale, or a free weigh at the post office all work. What you need is to know which side of an ounce line you are on.
Why a rough guess is not good enough
Postage moves in whole-ounce steps, and any fraction counts as a full ounce. An invitation at 1.05 oz costs $1.11, not $0.82. Guess low and the invitations are short paid; guess high and you overspend $0.29 on every one. On 150 invitations that is $43.50 either way.
So the goal is not the exact weight. It is a confident answer to one question: under or over the line?
Method 1: a kitchen scale
A digital kitchen scale is the best tool most homes already have. Switch it to ounces if it has the option, or use grams: 1 oz is 28.35 g, 2 oz is 56.7 g, 3 oz is 85 g and 3.5 oz is 99.2 g.
Kitchen scales are least accurate at very low weights, so do not trust a single reading of one envelope near the line. Use the next method to check it.
Method 2: weigh ten and divide
Assemble ten complete invitations, weigh the stack, and divide by ten. This multiplies the weight into the range where a kitchen scale is reliable and averages out differences between sheets.
If the stack of ten weighs 9.5 oz (269 g), each is about 0.95 oz and you are close enough to the line to worry: the heaviest one in the batch could be over. If ten weigh 8 oz, you are safely at 1 oz postage. If ten weigh 13 oz, you are safely at 2 oz.
Method 3: the post office counter
Any post office will weigh a piece of mail for free. This is the most reliable method, and the clerk can check the shape, thickness and stiffness at the same time. Many lobbies also have a self-service kiosk with a scale. Bring one fully assembled, sealed invitation.
Methods to skip
Balancing an envelope against coins on a ruler, or comparing it by hand with a stack of paper, can tell 1 oz from 3 oz. Neither can tell 0.95 oz from 1.05 oz, and that is the only distinction that matters. Bathroom scales are no use at this weight at all.
What to weigh
Weigh the finished piece: every insert, the reply envelope with its stamp, liner, band, seal, and the outer envelope sealed. Then put the weight into the postage calculator. If you land just over a step, here is what to trim.
Questions and answers
How do I weigh invitations without a postal scale?
Use a digital kitchen scale, weigh ten finished invitations together and divide by ten, or have one weighed free at a post office.
How many grams is a 1 oz letter?
28.35 grams. Two ounces is 56.7 grams and three ounces is 85 grams.
Will the post office weigh my invitation for free?
Yes. A clerk at the counter will weigh a piece of mail and tell you the postage at no charge.
Is a kitchen scale accurate enough for postage?
Usually, if it reads in grams or tenths of an ounce. Near an ounce line, weigh ten invitations together to be sure.