POSTKID
Help kids fall in love with the mail — free calculators for postage, delivery times, envelope and paper sizes, pen-pal time zones, stamp counts, and letter reading level, plus friendly guides to letter writing, pen pals, postcards, and snail-mail crafts for families and classrooms.
From working out postage and counting stamps to sizing an envelope, timing a pen pal’s reply across time zones, and checking how long a letter takes to read, PostKid pairs free hands-on mail calculators with friendly guides and a richly illustrated museum. Help kids fall in love with sending real mail.
Letter & Mail Tools
Free tools for every letter — postage calculator, mail delivery time estimator, envelope & paper size matcher, pen-pal time-zone helper, letter reading time, and stamp quantity calculator.
Postage Calculator
Weigh the letter, pick the class and destination, and get a friendly estimate of the postage — so a child knows how many stamps to grab before the trip to the mailbox
Mail Delivery Time Estimator
Choose how far the letter is going and the service, and see a range of days — perfect for answering the classic pen-pal question, when will it get there?
Envelope & Paper Size Matcher
Tell us the paper and the fold, and we name the envelope that fits with a simple fold guide — no more letters that won't go in or cards that arrive crumpled
Pen-Pal Time-Zone Helper
Compare two cities to see the hours apart and the shared window when both children are awake — the best time to write, call, or trade voice notes with a pen pal abroad
Letter Word Count & Reading Time
Paste a letter or enter its word count to see how long it takes to read at four ages, plus a note on whether its length suits a younger reader
Stamp Quantity Calculator
Enter the weight and the stamp you have, and see how many to stick on to cover the postage, plus the little leftover value — never guess at the mailbox again
Postal & Writing Museum
Wander an immersive museum of the mail and the craft of writing it — the stamps and postmarks collectors treasure, the post boxes and post offices that carry a letter, the letters and postcards themselves, and the pens, ink, and calligraphy behind the words, each in its own gallery, so kids can get to know the stories behind every stamp and envelope: how each thing came to be, what it does, and the little bit of history it carries.
Tour the museum →From the Mailbag
Fresh guides on letter writing, pen pals and postcards, stationery and snail-mail crafts, and classroom mail projects, plus practical tips for addressing, stamping, and sending a child’s first letters.
What Paying for Speed Actually Buys, Journey by Journey
Express saves 2 days on a letter across town and 16 days on one going abroad. The extra money is worth wildly different amounts depending on how far the letter has to go.
Posting Backwards From a Birthday
Cards arrive late because people post them forwards. Start at the date it has to arrive, subtract the slow end of the range, add a few days of slack, and the posting date works itself out.
What It Costs to Write Abroad, and Where the Multiple Bites Hardest
An international letter is 2.1 times the domestic price. A small package abroad is 2.7 times. The multiple is not constant — and knowing where it is worst decides what you send.
How Long Your Letter Takes to Read, and Who It Suits
A 400-word letter takes an adult 1.7 minutes and a six-year-old 5. Writing for a younger pen pal is mostly a question of length, and length is the easiest thing in the world to check.
Why a Pen Pal Replies Once a Month, Not Once a Week
An international letter takes 7–21 business days each way. Double it for the round trip, add a few days to actually write back, and a reply cycle is 3.8 to 9.4 weeks. Nobody is ignoring anybody.
Twelve Hours Apart Is Where the Conversation Gets Hardest
Up to twelve hours apart, every hour of time difference costs an hour of shared waking time. At twelve there is one hour left, and past that the window opens again on different calendar dates. That is the number that decides whether a friendship happens live or by post.
Keep Learning
Practical know-how on writing and addressing a letter, plain-language explainers on stamps, postmarks, and how the post moves the mail, and gentle ideas for pen pals and postcard swaps — everything a family or classroom needs to make snail mail a habit.
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