Poster Tiler: Split an Image Across A4 Sheets

What does a poster tiler do?

It cuts one image into a grid of A4-sized pieces and writes them into a PDF, one piece per page. You print the pages on an ordinary printer and join them, and the result is a poster several times larger than anything the printer could produce in one pass.

Everything happens in the page you are reading. The image is decoded, sliced and encoded into a PDF by your own browser, so nothing is uploaded and no account is involved.

How do you use it?

1. Upload the image you want enlarged
2. Pick a tile layout: 1 × 2, 2 × 2, 2 × 3, 3 × 3
3. Pick the sheet size. A4 is the default; choose US Letter and the whole poster is built for Letter instead
4. Pick how the image should fit the grid: crop to fill (the default), fit the whole image, or stretch
5. Set the overlap flap in millimetres. The default is 10 mm (0.4 in)
6. Download the PDF and print it at 100% on the sheet size you picked
7. Trim the flap off one sheet of each pair, line the sheets up and tape them from behind

Which layout gives which poster size?

An A4 sheet is 210 by 297 mm (8.3 by 11.7 in), so the grid decides both the size and the shape of the finished poster. The four layouts are not four sizes of the same rectangle — a 1 × 2 strip and a 2 × 2 block are quite different proportions.

The largest layout, 9 sheets in a 3 × 3 grid, finishes at roughly 578 by 837 mm (22.7 by 32.9 in) — about the size of a standard one-sheet film poster, from a printer that holds nothing bigger than a sheet of A4.

Why an overlap flap instead of a cut line?

Because butt joints show. If two tiles are trimmed to the exact edge of the image, every fraction of a millimetre you are off leaves a white gap or a doubled line, and a poster has a lot of seam to be off along. An overlap means the same strip of the image is printed on both sheets, so you slide one over the other until the picture matches and the join disappears into the artwork.

The flap is taken out of the image, not added to the paper. Each sheet still prints at 210by 297 mm, but neighbouring sheets duplicate a strip 10 mm wide on each side of the seam, which is why the finished poster is smaller than the sheets laid edge to edge. Raise the flap to 15 or 20 mm if you are gluing rather than taping and want room to slide a wet sheet.

Can I tile onto US Letter instead of A4?

Yes — pick US Letter in the sheet size selector and the whole poster is built for it. Letter is 216 by 279 mm (8.5 by 11 in) against A4's 210 by 297 mm: wider and shorter. Building for Letter from the start is the reliable route in the US and Canada, where A4 is the size that is hard to find.

If you already have an A4 PDF and only Letter paper, Fit to page will still work: it scales every tile by the same factor — about 94% — so the flaps go on lining up and the only consequence is a poster about 6% smaller than the figures above.

What you must not do is print an A4 PDF at Actual size on Letter. A4 is 18 mm taller, so actual-size printing clips that much off the bottom of every tile, and the bottom of a tile is exactly the strip the next row down has to overlap. The seams then have nothing to join to.

What if my image is a different shape from the grid?

Pick how it should fit. A 2 × 2 grid is about 1 : 1.4 width to height, so a 3:2 photo does not match it and something has to give.

• Crop to fill — the default. Keeps the proportions and trims the overflow evenly from both sides. Right for photographs
• Fit whole image — keeps the proportions, fits everything on and leaves white margins. Right for diagrams and logos, where the edges carry meaning
• Stretch to fill — distorts the picture but throws away no pixels

Crop the image to the grid's ratio before uploading and all three give the same result. The photo print layout tool is the opposite job — many photos onto one sheet at a true physical size — and is the right one if you wanted copies rather than an enlargement.

Notes

• Tiles are rendered at 150 dpi, which is about what a domestic inkjet resolves on plain paper at poster viewing distance
• Every sheet is rendered at the same scale, including the layouts with a middle row or column (2 × 3 and 3 × 3). Middle sheets carry a flap on both sides and edge sheets only on one, so the edge sheets leave a thin white margin on the outside of the poster rather than being blown up to fill the paper. That margin is the outer border of the finished piece, and it is what keeps the seams meeting at one scale
• Source resolution matters more than the layout. A 2 × 2 poster is rendered 2,480 px across, so an image narrower than that is being enlarged and will look soft
• The output is one PDF with 4 to 9 pages; print it as you would any document, or hand the file to a copy shop
• Merging that PDF with another, or pulling single pages out of it, is the merge and split tool
• The image never leaves your browser, so unreleased artwork is safe to tile here

Where these figures come from

The rules and figures this page relies on come from the sources below (links checked 25 September 2026).

• ISO 216:2007, Writing paper and certain classes of printed matter — Trimmed sizes — A and B series — International Organization for Standardization
• ASME Y14.1, Drawing Sheet Size and Format — The American Society of Mechanical Engineers

What can change: Both sheet standards have been stable for decades; a revision would change the edition, not the millimetres quoted here.