How to print an A1 poster on A4 paper

By Sebastian Sajoux · Updated August 2026

A1 measures 594 x 841 mm. A4 measures 210 x 297 mm. Eight A4 sheets — four across, two down — cover 840 x 594 mm, which is an A1 to within a single millimetre. Like every other step in the ISO series this is designed, not lucky, and it means an A1 poster is really just an eight-page A4 document that has not been cut up yet.

The layout: four across, two down

Halving works down the whole series. A1 is two A2, four A3, eight A4. In grid terms, a landscape A1 becomes four portrait A4 sheets across by two down: 4 x 210 = 840 mm wide and 2 x 297 = 594 mm tall. A portrait A1 is the same grid rotated — two across by four down.

This is the largest split most people should attempt on a home printer, and the reason is not the printing. It is that eight sheets produce ten interior seams, and a poster this size gets handled, rolled, and mounted, all of which stress every joint you made.

Overlap is mandatory at this size

On a two-sheet split you can get away with butt joints. On eight you cannot. Set 0.5 in of overlap and let the tool repeat a strip of image on each neighbouring tile. Two reasons this matters more as the poster grows:

• Error compounds along a row. A half-millimetre misalignment on the first seam is invisible. The same error repeated across four sheets puts the far edge two millimetres out of true, and that is visible on a straight line running through the artwork.
• Overlapped joins are stronger. A butt joint is held together by tape alone. An overlapped joint has paper bonded to paper across a 12 mm band, which survives rolling and mounting far better.

The cost is size: overlap consumes image area, so the finished poster comes out slightly under a true A1 unless you set the size by width instead of by page count. If exact A1 matters — for a frame, or a competition entry — set the driver to Width (inches) and enter 23.4, then let the tool decide how many sheets it needs.

The split, step by step

1. Drop the A1 artwork into the splitter. Vector PDFs are ideal here; they re-render at print resolution instead of stretching.
2. Set paper to A4, margins to 0.25 in, and quality to Best (300 dpi) — at this size the file is large either way, and you may as well have the detail.
3. Set Pages across: 4 for a landscape A1, or Pages down: 4 for portrait. Confirm the readout says eight pages before you export.
4. Set overlap to 0.5 in and leave cut guides on.
5. Export the eight-page PDF. Print at 100% / Actual size on A4, and print all eight in one run so paper and ink stay consistent — colour drifts between cartridges and even between sessions.

Assembling something this big without wrecking it

Clear a table bigger than the poster, or work on the floor. Assemble in rows first — join the top four sheets into a strip, then the bottom four — and join the two strips last, in a single long seam. That one long seam is easier to get straight than four short ones stacked vertically.

Tape from behind with one continuous strip per seam rather than a series of short pieces, which show as ridges under angled light. If the poster is going on a wall permanently, mount it to foam board while it is flat; an A1 sheet of taped paper will not stay flat on its own.

Resolution: be honest before you spend eight sheets

A1 is 23.4 x 33.1 inches. At 200 DPI that wants roughly 4680 x 6620 px; at 300 DPI, about 7020 x 9930 px. Very few photographs are that large natively. In practice:

• Vector artwork or a PDF export from design software — no problem at any size.
• A modern full-frame or high-end phone photo — fine at 150 to 200 DPI, which is genuinely sharp for something viewed from more than a metre away, and an A1 poster always is.
• A web image or screenshot — do not. Eight sheets of visible pixelation is an expensive lesson. Run it through the upscaler first and check the DPI readout, or pick a smaller finished size.

If you have an A3 printer

Four A3 sheets in a 2 x 2 grid also make an A1, with four seams instead of ten. If A3 is available to you, take it every time — fewer joints is always the better poster.

Other A-size splits