The Pen-Pal Exchange Kit

The PostKid plan for running a child's pen-pal mail, at home or for a whole class: safe addresses, letters that mail at the letter price, and a calendar that fits the school year

PostKid's free Envelope & Paper Size tool finds the envelope a folded sheet fits, and the Postage and Stamp Quantity calculators ask you which class of mail it is. But the envelope decides the class: its size, its shape and what is inside it. The Mail Delivery Time estimator answers one way, while a pen-pal exchange is a round trip. The tools never meet, and a class multiplies every mistake by the number of children. This kit, written for parents and teachers, joins them. A Letter sheet mailed flat pays $1.69 as a large envelope; folded in three it is a $0.82 letter. A square card or a taped coin adds a $0.49 surcharge, and a friendship bracelet can make a letter a parcel. In the worked example, 24 letters abroad at $1.75 each are $42.00, while one large envelope between two schools is $8.75, and no child's home address goes on anything. Waiting for each reply abroad fits 3 exchanges into a 30-week season at the slow end; posting every four weeks fits 7. Step 1 is the safety frame: letters travel between adults' addresses, first names only, an adult reads every letter, pen pals never meet, and any call is booked by the adults. Prices are USPS retail prices effective July 12, 2026, so check the current rate before you buy; worked figures are examples, computed by the site's own calculators. 23 printable pages: seven steps, an exchange plan, an envelope check, a class mail log, a USPS price card and a quickstart, plus a personalised sheet worked from the settings you entered in the calculator you came from.

Look inside

Two full pages from the kit, exactly as printed. Click either to read it at full size before you decide.

What is in it

• The Adult's-Address Rule: school, program or parent addresses, first names only, adults read every letter, no meeting and no moving to apps
• The Fold-to-a-Letter Rule: which folds mail at the letter price, and what a flat sheet costs as a large envelope
• The Flat-and-Bendy Rule: what a square card, a taped coin or a friendship bracelet does to the class and the price
• The Forever Rule: sheets per ounce by paper weight, and paying with the stamps you already have
• The Calendar Rule: the round trip at the slow end, and why posting every four weeks beats waiting for replies
• The One-Envelope Rule: a class's letters in one large envelope between two schools, priced by class size and season
• The Adults-Book-It Rule: waking and school-hours call windows on both clocks, booked and supervised by adults
• An exchange plan, an envelope check and a class mail log to print, first names or class codes only
• A USPS price card (July 12, 2026) with the letter, large-envelope and postcard size classes
• A personalised sheet: your envelope and the price it decides, your stamps, your round trip and posting calendar, and your call window

The kit picks up where the free Envelope & Paper Size toolleaves off. The tool finds the envelope a folded sheet fits; the kit shows what that envelope costs to post, because the envelope, its shape and what is inside decide the mail class. It is written for parents and teachers: letters travel between adults’ addresses with first names only, then fold to a letter, stay flat and bendy, are stamped with the stamps you already have, go out on a posting calendar planned at the slow end, travel as one envelope between two schools, and any call is booked by the adults. Prices are USPS retail prices effective July 12, 2026; they change, so check the current rate before you buy stamps. The worked class and weights are examples. The kit matches no one with a pen pal and does not replace a school’s or program’s safeguarding policy.