Paper Scale Calculator

Choose a from size and a to size. The calculator gives the percentage to type into the print dialog, whether the page needs rotating, and how much margin is left over.

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The ISO shortcut

ISO sizes share the same 1:√2 proportions, so scaling between them never crops anything. One step is 141% up or 71% down; two steps are 200% or 50%. Print dialogs on many office copiers have these presets built in for exactly this reason.

Mixing ISO and North American sizes

Letter and Legal do not share proportions with A4, so there is always a little white space somewhere. The calculator picks the largest percentage at which the whole page still fits, then tells you how much margin remains on each axis. If you would rather fill the sheet and lose a strip at the edges, use the aspect ratio checker to see what gets cut.

Worked example

A poster designed at A2 needs to go on an A4 office printer for proofing. A2 to A4 is two steps down: 50%. The preview shows the A2 outline in dashed ink and the scaled page in vermilion on top, so you can see they line up exactly.

Questions about this tool

What percentage is A4 to A3?

141%. Every step up the ISO A series is √2, or 141.4%; every step down is 71%. A4 to A5 is 71%, A3 to A4 is 71%, A4 to A2 is 200%.

How do I print A4 on Letter?

Set the scale to 94%. Letter is shorter than A4 by 18 mm, so the page has to shrink slightly; the sides then have 6 mm of extra room. Going the other way, Letter onto A4, is 97%.

Why does it say rotated?

Some pairs fit better sideways. Two A5 sheets make one A4 only when they are turned, and the same logic applies when the target sheet's proportions differ from the original.

Is fit-to-page the same thing?

Usually. Fit-to-page in most print dialogs calculates this same best-fit percentage, but it may also shrink the page to keep inside the printer's non-printable margin. Typing the percentage yourself gives you control.

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