How it works
What is listed
120 sizes in thirteen series: ISO A, B and C (C is for envelopes), the RA and SRA press sheets, US office sizes (Letter, Legal, Tabloid and others), US ANSI and architectural sizes, Japanese JIS B, Chinese D, Swedish SIS, and the traditional French and British Imperial sheets.
Sizes are stored in millimetres as their standards define them; US office sizes are stored in inches. Every other unit is converted from those.
Units and pixels
Inches divide millimetres by 25.4. Eighths round to the nearest ⅛ inch and are marked ≈ when that rounding is more than 0.01 inch off. Points are 72 to the inch, the unit of PDF pages and design apps. Pixels depend on the print resolution you pick: 72, 150, 300 or 600 DPI.
inches = mm ÷ 25.4; points = inches × 72; pixels = round(inches × DPI)
Finding and comparing
Type a name to filter the list, or a size to see the five closest standard sizes with how far each is off, turned either way. Sizes in pixels need a DPI (2480x3508@300dpi). Bare numbers both under 50 are read as inches. Opening an image reads its pixel size; opening a PDF reads the first page's MediaBox.
Each size you pick fills sheet 2, then sheet 1, in turn. The two are drawn to one scale, stacked, side by side or one above the other, with the ratio of their areas: A4 is half of A3, so the ratio is 2×.
