Paper sizes explained — A4, Letter, A5, B5 and the rest

Two families of paper

Almost every printer on earth is loaded with one of two sheets: A4 (210 × 297 mm) or US Letter (8.5 × 11 inches). They look interchangeable in a stack, but they come from completely different design ideas. The international sizes, defined in the ISO 216 standard, are generated by a single rule and scale cleanly from postcard to poster. The North American sizes grew out of traditional paper-mill formats and are defined in whole and half inches.

For ordinary documents the difference barely matters, because word processors reflow text to fit. For printable paper it matters a great deal. A graph-paper PDF draws its lines at exact positions on an exact page, so the page size in the file has to match the sheet in the printer or the grid gets cropped or scaled.

How the A series works

The A series rests on one property: every sheet has sides in the ratio 1 : √2 (about 1 : 1.414). Cut such a sheet in half across its long side and each half has exactly the same proportions as the original. No other rectangle does this.

The starting point is A0, defined as one square metre in area with that √2 ratio, which works out to 841 × 1189 mm. Halve it and you get A1; halve A1 and you get A2; and so on down the line. Each step halves the area, so:

• two A4 sheets side by side make an A3;
• an A4 folded in half is two A5 pages;
• an A4 sheet is exactly 1/16 of a square metre.

That last fact is why paper weight in grams per square metre is so handy: a standard 80 g/m² A4 sheet weighs 5 grams.

The √2 ratio also makes enlarging and reducing painless. A photocopier set to 141% turns A4 into A3 with nothing cropped, and 71% goes the other way. A drawing on A4 stays in proportion when printed on A3, though of course a 5 mm grid becomes a 7.07 mm grid in the process — fine for a poster, not for a true-scale sheet.

The B series and the JIS variant

The B series fills the gaps between A sizes. Each B sheet has the same √2 shape, with dimensions that sit at the geometric mean of the A sizes either side, so B5 is bigger than A5 and smaller than A4. B0 has a short side of exactly one metre. B sizes are common for books, posters and especially notebooks: B5 is a popular student notebook size in Japan, Korea and parts of Europe.

Japan’s industrial standard (JIS) defines its own B series with slightly larger sheets. JIS B5 is 182 × 257 mm against ISO B5’s 176 × 250 mm. If a Japanese notebook says “B5”, assume JIS. In the generator these are separate choices, B5 and B5 (JIS).

North American sizes

The inch-based sizes do not share a common ratio, so they don’t scale into each other:

• Letter (8.5 × 11 in) is the standard office and school sheet, ratio about 1.29.
• Legal (8.5 × 14 in) is the same width as Letter but three inches longer, used for contracts, legal pads and long lists.
• Tabloid / Ledger (11 × 17 in) is two Letter sheets side by side, so Letter does halve into it neatly. It is also called ANSI B.
• Half Letter or Statement (5.5 × 8.5 in) is Letter folded in half — the North American planner and booklet size.
• Executive (7.25 × 10.5 in) turns up in some notepads and stationery.

Letter is the norm in the United States and Canada and in Mexico and several other Latin American countries, and is widely used in the Philippines. Nearly everywhere else uses A4.

Size chart

The generator also offers index cards (3 × 5, 4 × 6 and 5 × 8 inches) and a 3.5 × 5.5 inch pocket memo-book size.

Why the mismatch matters for grids

Put an A4 PDF on Letter paper and one of two things happens. At 100% scale, about 18 mm disappears off the bottom of the page. With Fit to page, the driver shrinks everything to roughly 94% to squeeze the height in, and a 5 mm grid prints at about 4.7 mm. Going the other way, Letter content on A4 loses a few millimetres at the sides.

Neither is acceptable for something meant to be measured, so pick the paper you actually have before downloading. If you are not sure what is loaded, measure the short edge: 210 mm means A4, 216 mm (8½ inches) means Letter. Our guide to printing at actual size covers the dialog settings on every common device.

Printing A5 booklets from A4

Because A5 is exactly half of A4, you can make a stapled or stitched A5 notebook with a home printer:

1. Choose A5 as the paper size and set up the ruling you want.
2. In Advanced options, set Pages in the PDF to the number of notebook pages, then switch on Booklet. The generator imposes the pages two-up on A4 in the right order, padding the count to a multiple of four.
3. Print double-sided, flipping on the short edge, at 100%.
4. Stack the sheets, fold the stack in half, and staple or sew along the fold.

The same trick works for Half Letter on Letter, A6 on A5, B6 on B5 and B5 on B4. For more than about ten sheets, fold them in a few smaller bundles (signatures) and nest or sew them together, otherwise the inner pages stick out past the outer ones.

How much fits on each size

The page size decides how much grid you get. These counts come straight from the generator, with its default margins (half an inch on inch sizes, 10 mm on metric ones), so they are exactly what prints:

Two things stand out. Legal holds about a third more grid than Letter for the same width (2,508 squares against 1,900 at 5 mm), and an A5 or Half Letter page holds a little under half of a full sheet: margins take a bigger share of a small page.

Choosing a size for a printable

A few rules of thumb:

• Everyday graph, dot or lined paper — whatever is already in your printer, A4 or Letter.
• Planners and journals — A5 or Half Letter, printed as a booklet.
• Big diagrams, maps and posters — Tabloid or A3 if your printer takes it, otherwise tile Letter or A4 pages.
• Long lists and legal-pad style notes — Legal.

Whatever you choose, the spec table on each page shows exactly how many squares, dots or lines fit, so you can compare sizes before you print.