Sophie Atkinson
What Bleed Really Means
Bleed is the extra artwork that sits beyond the final cut line. If your design has colour, a photograph, or a pattern that runs to the edge of the finished piece, you need that colour to extend past the edge, so that when you trim the sheet you are cutting through ink rather than through blank paper.
The standard bleed in UK printing is 3mm on every side. So a design intended to finish at A5 (148 × 210mm) with edge-to-edge colour should be set up at 154 × 216mm, with the trim line marked 3mm in from each edge. Any element that must not be cut — lettering, logos, fine line work — should sit at least 5mm inside the trim line, which gives you a safety margin.
In short: bleed protects the edges, the safety margin protects the content. They do different jobs and you usually need both.
Why Your Home Printer Needs a Safety Margin
Domestic inkjets and laser printers cannot print to the very edge of a sheet. Most leave an unprintable border of roughly 3mm at the sides and top, and often considerably more at the bottom — some models need 10 to 15mm of clear space along the trailing edge because the paper has to be gripped by rollers.
Anything you place inside that unprintable zone will either be cropped, shifted, or quietly scaled down by the printer to fit. That is how a carefully centred design ends up 4mm off to the left. If you are printing directly onto the final sheet rather than trimming afterwards, treat 10mm as your minimum margin, and 15mm if you want the layout to feel calm and deliberate.
Setting Up Bleed and Margins Before You Design
Adding bleed later is fiddly and rarely tidy. Set it up at the very start, when you create the document. In the document setup panel of your design software, enter the finished size, then a bleed value of 3mm on all sides. Turn on ruler guides for the trim line and a second set 5mm inside for the safety margin.
Work out which of the two situations you are in before you begin:
- Trimming after printing: you need bleed, because you will cut the sheet down to size and the artwork must overshoot the cut.
- Printing straight onto the finished sheet: you do not need bleed, but you do need a generous margin of at least 10mm, because nothing can reach the edge anyway.
UK Paper Sizes and Common Bleed Figures
Worth keeping to hand: A6 is 105 × 148mm, A5 is 148 × 210mm, A4 is 210 × 297mm, A3 is 297 × 420mm, and DL is 99 × 210mm. Add 3mm of bleed to each side, so an A4 piece with edge-to-edge artwork becomes 216 × 303mm.
Greetings cards catch people out. A card that folds to A6 is usually printed flat on A5 and folded in half, so the flat artwork needs to be 154 × 216mm with bleed if any colour runs off the edge. For larger posters, bleed often increases to 5mm, simply because a bigger sheet is harder to trim accurately. If you are stitching a booklet, remember that inner pages shift slightly when folded, so give the centre of the spread a little extra breathing room.
Borderless Printing: What Your Printer Will Actually Do
Many home printers offer a borderless or edge-to-edge setting, but it usually works only on certain photo papers and only at selected sizes. Even when it is available, the printer may enlarge your artwork by one or two per cent to push the image past the edge, which throws out alignment and can clip text near the margins. It also tends to change how colour is handled.
A more reliable route for makers is to print onto a larger sheet and trim down. Print your A5 design on A4, leaving plenty of room, then cut to size with a steel rule and a fresh blade. You get true edge-to-edge colour, clean straight edges, and complete control over the final dimensions.
A Practical Pre-Print Checklist
- Confirm your document size against the final trimmed size.
- Add 3mm bleed on every side where colour or imagery reaches the edge.
- Keep all text and important detail at least 5mm inside the trim line.
- Run one test print on plain paper at 100% — never use "fit to page" or "scale to fit".
- Check your printer's unprintable margins, especially the bottom edge.
- Allow ink to dry fully before trimming, particularly on coated or textured stock.
- Trim on a cutting mat with a sharp blade and steel rule, in two or three light passes rather than one heavy push.
- For folded cards, check the paper grain runs in the same direction as the fold to avoid cracking.
Get into the habit of building bleed and margins into your setup, and the trimming stage becomes the satisfying part of the process rather than the moment something goes slightly wrong.
