Paper size converter
Compare paper sizes by area: how many A4 sheets make an A1, what US Letter is closest to, and the dimensions of every A size.
That's about the same as an A4 sheet. With ISO proportions that is a sheet of about 210.2 × 297.3 mm (8.277 × 11.7 in).
What it means
How big is that sheet?
ISO 216 sizes are rounded to whole millimeters on real sheets. US sizes are compared by area; their proportions differ from √2.
Every unit
That sheet in every system
Learn
Three things worth knowing
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Each step halves
A3 is two A4s, A2 four, A1 eight, A0 sixteen. A5 is half an A4.
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Lichtenberg’s ratio
Georg Lichtenberg noted the √2 ratio in 1786; Germany standardised it as DIN 476 in 1922, and it became ISO 216 in 1975.
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Letter is not A4
US Letter (216 × 279 mm) is wider and shorter than A4 (210 × 297 mm); printing one on the other crops the edges.
Shortcuts
Popular sheet conversions
Background
About ISO paper sizes
ISO 216 paper keeps its sides in the ratio 1 : √2, so folding a sheet in half gives the next size with the same shape. A0 is one square meter; A1 is half of it, and A4 (210 × 297 mm) is a sixteenth.
B sizes sit between the A sizes, and C sizes are envelopes: a C4 envelope takes an A4 sheet flat.