What is trim size?

The size that survives the cut

Commercial printing rarely prints a flyer on a sheet of exactly the right size. It prints several pieces on a larger sheet, then trims them out with a guillotine or digital cutter. The line where that blade cuts is the trim line, and the rectangle it leaves is the trim size. Vistaprint's help centre puts it simply: trim size is the area of the artwork that will definitely appear on the final printed product. The term applies to anything cut after printing. Book publishers use it for the page dimensions of a finished book, printers use it for flyers, cards and posters, and packaging uses it for the flat size of a box before folding. In every case it is the number that describes the object, not the file.

Trim size, bleed size and safe area

Three measurements sit around the same design. The trim size is the finished page. The bleed size, sometimes called document size, adds extra artwork beyond the trim so colour runs to the edge after cutting; Vistaprint's guide to crop marks gives the standard bleed as 0.125 inches, or 3 millimetres, beyond the trim line, which turns an A4 trim of 210 by 297 millimetres into a document of 216 by 303. The safe area sits inside the trim and is where text belongs. Crop marks, when used, are short lines outside the corners that show where the trim falls. A design with no colour at the edges can be supplied at exactly the trim size, with no bleed at all.

When trim size decides the job

Trim size drives cost, because it determines how many pieces fit on each press sheet. Standard sizes like A4, A5 and DL impose efficiently and are cheaper per piece than an unusual size that wastes paper. It decides fit: envelopes, display racks, frames, letterboxes and binders are all made for standard trim sizes. It determines readability, since the same text shrinks or grows with the page. For books, the trim size affects the page count and the spine width. And it has to be stated precisely when ordering. A shop that receives a file at 216 by 303 millimetres needs to know whether that is an A4 design with bleed or an unusual size to be printed as supplied.

Common mistakes

The most common is designing at the bleed size and placing text right up to the edge of the document, forgetting that 3 millimetres on each side will be cut away. The second is quoting a size in inches to a shop that works in millimetres, or the reverse, and letting rounding change the result. The third is sending a file at a shape that does not match the ordered trim size, such as a square design for a rectangular flyer, which forces the printer to crop or pad. The fourth is confusing trim size with the paper size the printer runs, which is always larger. The last is assuming a digital preview shows the finished edge exactly; it shows the file, and the file is not the trimmed piece.

Trim size in the flyer builder

Every canvas in the flyer builder is a trim size with nothing added. A4 portrait is 1240 by 1754 pixels on the canvas and exports at 2480 by 3508, which is exactly A4 at 300 DPI and exactly the finished page. There is no bleed extension, no crop marks and no trim line drawn on the canvas, and no DL, A5 or other print size to choose from, only A4 portrait and landscape alongside six social sizes. When ordering, tell the shop the export is A4 at trim size with no bleed. If the design keeps a clear margin at every edge, most shops print it as supplied. If colour runs to the edge, ask how they handle a file without bleed, since some scale it up very slightly and some ask for a new file.

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