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A Guide to Paper Sizes: A4 vs. Letter
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Design ProWhy doesn't paper fit in the printer? The logic behind the ISO 216 standard versus American Letter size.
The A-series paper sizes (A4, A3, etc.) are a marvel of mathematical beauty. The ratio of the sides is the square root of 2 (approx 1.414).
The Magic of Root 2
This unique ratio means that if you cut an A4 sheet in half, you get two A5 sheets with the exact same aspect ratio. This makes scaling documents up and down seamless.
US Letter
The US, Canada, and parts of Mexico use 'Letter' size (8.5 x 11 inches). It's slightly wider and shorter than A4, which can cause headaches when printing international documents.
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Design Pro
Contributing writer at MetricConv, covering measurement science, unit history, and practical conversion guides.
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