Bingo Card Generator

Why a batch of "random" cards can still tie

A 5 × 5 card with a free centre has 24 playable squares. If your list has exactly 24 items, every card in the batch holds the same 24 items — only the positions move. Line bingos still land at different moments, because the lines contain different items, but a blackout game finishes on the same call for every child in the room. Nothing on the card tells you that in advance, which is why this page prints the numbers before you commit paper to it.

Two of the figures printed under the controls matter here. The first is how many different sets of items a card can be drawn from — 24 items gives exactly one, 30 items gives 593,775, and it climbs steeply from there. The second is the average overlap: with a list of length N and cards of K squares, two cards share about K² ÷ N squares. Twenty-four squares drawn from 30 items overlap on roughly 19 of them; drawn from 60 items, on about 10. Overlap is what produces three hands in the air at once. If you want one clear winner, the lever is a longer list, not more cards.

Reprinting card 14 after it goes missing

Every batch is built from a seed, and the seed is printed in the corner of each card next to its number. Leave the seed box blank and a fresh one is drawn for you; type it back in later with the same list and the same settings and the exact same batch reappears, card for card. So when a card is left on the bus, you reprint that one child's card rather than reissuing thirty. Change the list, the grid or the free-space setting and the batch changes with it — the seed only reproduces a batch when everything else matches.

Getting it onto paper

Press Print and the browser's own print dialogue opens. The controls, this text and the ad placeholder are all suppressed; only the cards and the caller's list go to the printer. Choose one, two or four cards per page — two is the usual choice for a class set on A4 or Letter, four suits younger children who need fewer squares. Cards never split across a page break. The caller's list always starts on a fresh page at the end, listing every item in draw order and numbered, so you can tick as you go and check a claimed line afterwards.

There is no PDF export here. Your browser's print dialogue has a "Save as PDF" destination that produces a cleaner file than an in-page PDF library would, and it costs the page no download weight. If margins look tight, turn off headers and footers in that dialogue.

Questions people ask after their first batch

How many items do I need for a class of thirty?

Twenty-four is the minimum for a 5 × 5 card with a free centre, but it is a poor minimum for the reason above. Somewhere between 40 and 50 items gives cards that differ visibly while keeping a game to a sensible length. If you only have 20 words for a spelling unit, drop to a 4 × 4 grid — sixteen squares, no free centre — instead of padding the list with filler.

Are duplicate cards really impossible?

Within one batch, yes: each card's full layout is compared against the ones already made and a repeat is discarded and redrawn. If the list is too short to supply the number of cards you asked for, the tool stops and says how many it managed rather than padding the batch with copies. Across two separate batches generated at different times, a repeat is possible in principle, though with a list of any reasonable length it is vanishingly unlikely.

Does it make classic 75-ball bingo cards?

Switch the card type to Numbers. The grid fixes at 5 × 5 and each column is drawn from its traditional range — B from 1–15, I from 16–30, N from 31–45, G from 46–60, O from 61–75 — with the free square in the middle of the N column. The caller's list then covers all 75 balls, labelled with their column letter.

Where do the cards get made?

In the page, on your machine. The generator is a few kilobytes of JavaScript that runs after the page loads; your list is never sent anywhere, and after the first load the page keeps working with the network off. Nothing is saved either, which is the trade-off: close the tab and the batch is gone unless you noted the seed.

Honest limits

No images. Picture bingo needs uploads and a layout engine, and this page has neither, so a picture round means writing the prompt in words. Long entries shrink to fit but a whole sentence in one square will look cramped — aim for four words or fewer. The shuffling uses a small seeded generator (mulberry32) rather than the browser's cryptographic source, because reproducing a batch from a seed requires it; it is more than good enough for dealing bingo squares and unsuitable for anything where the outcome is worth money.