Paper Size & Fold
ISO A, B, C sizes from the standard’s rule, US Letter / Legal / Tabloid / ANSI, fold panels (half, letter, Z, gate, accordion, French) and pieces per sheet.
The sheet in mm and inches with area and ratio, the full ISO table, panel widths and folded size for the chosen fold, and how many pieces of another size cut from the sheet.
Example: A4 with a letter (tri-) fold and a 2 mm allowance: panels 70.7 / 70.7 / 68.7 mm; four A6 cards cut from one A4 with 0.3 % waste; Letter landscape gate fold: flaps 68.4 mm, middle 142.7 mm.
A0 is a square metre;
the rest is halving.
How the ISO sizes are computed rather than looked up, the US sizes, how folds split a sheet, and what a fold allowance is.
ISO 216 by rule
The A series starts from a sheet of one square metre with sides in the ratio 1 : √2 — 841 × 1189 mm after rounding — and each next size halves the long side, rounded down to the millimetre; that single property means A5 is half of A4 with the same proportions. B0 is 1000 × 1414 mm (the geometric mean between A sizes) and C0, the envelope series, is the geometric mean of A0 and B0. The page computes all three series from those rules and matches the standard's table exactly.
North American sizes
Letter (8.5 × 11 in), Legal (8.5 × 14 in), Tabloid / Ledger (11 × 17 in) and ANSI C–E (17 × 22, 22 × 34, 34 × 44 in) are defined inch sizes with no common ratio; they are converted at 25.4 mm to the inch. A custom size takes any width and height in mm or inches.
Folds and pieces
A fold divides the width into panels: half (2), letter or tri-fold (3, the inner panel shorter by the allowance you enter so it tucks in), Z (3 equal), gate (two flaps folding to the middle, each a quarter less the allowance), accordion (N equal) and French (half, then half again → 8 pages). The folded size is the largest panel by the full height. Pieces per sheet counts whole pieces in both orientations and reports the better one with the waste — no guillotine sequence or gripper margin is modelled. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- ISO 216: A0 = 1 m² with sides in ratio √2, B0 = 1000 × 1414 mm, C0 = geometric mean of A and B, each next size halves the long side rounded down; ANSI/ASME Y14.1 inch sizes
Last reviewed 21 September 2026. How results are checked: How we verify.