24 doors. 24 little threads.
A free puzzle advent calendar for adults who like numbers. One path puzzle a day.
Every tile once, sums in order.
The calendar
Door 13 × 3
What is a puzzle advent calendar?
A puzzle advent calendar gives you one small puzzle for each day of December up to Christmas Eve, usually 24 in all. Ours is free and online: each door opens on its date and holds a number-path board. Trace one path through every tile so the running sums hit the targets in order.
Doors open by your device's date, from December 1 to December 24. Before December 1, door 1 opens early as a preview. Boards grow from 3 × 3 (doors 1–8) to 3 × 4 (9–16) to 4 × 4 (17–24), and every one is built from a real path, so every door can be solved. Your solved doors are remembered in this browser only.
Advent itself starts earlier than the calendar. The US Conference of Catholic Bishops describes it as the four Sundays leading up to Christmas, beginning on the Sunday closest to November 30, which is November 29 in 2026. Most advent calendars, like this one, simply count December 1 to 24.
One door a day, 24 days, no sign-up.
How to play a door
Start on the tile marked START. Tap a neighbouring tile (up, down, left or right) to extend the thread. Your running total must land exactly on the first target; that tile gets an orange ring and the count starts again from zero for the next target. The last target has to finish on the last unused tile. Dashed borders show where you can go next; orange borders show a tile that would hit the target exactly. Tap any earlier tile on your path to go back to it.
Every tile, no diagonals, no repeats, sums in order.
What Sumthread looks like
Our design decision: the app has one rule and no timers. Boards are built for a thoughtful five-minute break, and finishing with zero hints and zero undos earns the Clean Weave seal.
Who should pick something else
- If you want a physical calendar to open each morning, buy a printed puzzle advent calendar. Ours lives in a browser tab.
- If you prefer word puzzles, this is all numbers and adding.
- If you want 24 hard puzzles, the early doors here are gentle on purpose. The app's 4 × 4 Deep Weave and 4 × 5 boards are the harder ones.
- Honest limit: this calendar is a web page, not the app. Progress lives in this browser and is lost if you clear site data. The app saves every board on your device and works fully offline.
Advent puzzle options, side by side
Use the page in December, keep the app for January.
Mini-story: the coffee door
Picture the first week of December. The kettle takes about four minutes, so that is when the door gets opened. A 3 × 3 takes a minute; the thread snaps into place and the ring glows on the last tile. By door 17 the boards are 4 × 4 and the coffee goes a little cold, which is part of the fun. On December 26 the habit is still there, so the next board comes from the Daily Thread in the app.
The best advent habit fits inside something you already do.
Advent calendar questions
When should I open the first door?
On December 1. Doors open by your device's date, and door 1 is open early as a preview so you can learn the rules.
Is this puzzle advent calendar really free?
Yes. There is no sign-up, no email and nothing to buy. Sumthread, the app the puzzles come from, is free too, with no ads.
Can I catch up on missed doors?
Yes. Every door from December 1 up to today stays open, so you can play several at once.
Where did advent calendars come from?
Lutherans first used them in the early 19th century, and early printed calendars hid Bible verses behind small cardboard doors, according to Wikipedia's history of the advent calendar.
Does the Sumthread app need internet?
No. It is 100% offline with no account, no ads and no third-party tracking.
Background: Advent calendar, Wikipedia.
Get Sumthread free. A thread for every day.
Five puzzle collections, a Daily Thread and five board themes, from Warm Ivory to Charcoal Dark.
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