Dimensions

• A3 dimensions in millimetres are 297mm x 420mm.
• A3 dimensions in inches are 11.7in x 16.5in.
• A3 area in square metres is 0.12474m²
• A3 area in square millimetres is 124740mm²
• A3 area in square feet is 1.34269ft²
• A3 area in square inches is 193.347387in²

Aspect Ratio

• The aspect ratio (width:height) of A3 paper is 1:1.4142 (1:√2).

Comparison With Other ISO 216 Sizes

• A3 is one eighth of the size of A0.
• A3 is one quarter of the size of A1.
• A3 is half of the size of A2, having the width of A2 as its height in portrait orientation.
• A3 is twice the size of A4, having the height of A4 as its width in portrait orientation.
• A3 is four times the size of A5
• A3 is eight times the size of A6.
• A3 is sizteen times the size of A7.
• A3 is thirty two times the size of A8.
• A3 is sixty four times the size of A9.
• A3 is one hundred and twenty eight times the size of A10.

Comparison With Non ISO 216 Sizes (Including US Sizes)

• A3 is the closest ISO 216 paper size to US Ledger, Tabloid and ANSI B being 0.5in shorter and 0.7in wider in portrait format. It is about twice the size of US Letter and Legal paper.

Weight of A3 Sheets

• A sheet of 80gsm A3 paper weighs 10 grams (0.35274 ounces).
• A sheet of 100gsm A3 paper weighs 12.5 grams (0.44092 ounces).
• A sheet of 160gsm A3 card weighs 20 grams (0.70548 ounces).

More details on paper weights, including a calculator for all grammages here.

Envelopes For A3 Paper

• A C3 envelope will take an unfolded sheet of A3 paper.
• A sheet of A3 paper folded in half by placing the two narrow sides together will fit into a C4 envelope.
• A sheet of A3 paper folded into quarters will fit into a C5 envelope.

Full information on ISO 216 envelope sizes here.

Untrimmed Sizes To Allow For Print Bleed

• RA3 (Raw format A3) is 105% of the size of A3, thus 305 x 430 mm (12.0" x 16.9").
• SRA3 (Supplementary raw format A3) is 115% of the size of A3, thus 320 x 450 mm (12.6" x 17.7").

More information on raw format and supplementary raw format here.

Magnification Factors For Reprographics & Photocopying

• Enlarge A3 to A0 using a scale factor of 283%.
• Enlarge A3 to A1 using a scale factor of 200%.
• Enlarge A3 to A2 using a scale factor of 141%.
• Reduce A3 to A4 using a scale factor of 71%.
• Reduce A3 to A5 using a scale factor of 50%.
• Reduce A3 to A6 using a scale factor of 35%.
• Reduce A3 to A7 using a scale factor of 25%.
• Reduce A3 to A8 using a scale factor of 18%.
• Reduce A3 to A9 using a scale factor of 12.5%.
• Reduce A3 to A10 using a scale factor of 8.8%.

More about magnification factors for reprographics and photocopying here.