I have this expression:

12 × 3 mm².

I guess that it should not be pronounced as "twelve multiplied by three millimeters squared". I've tried to google it already but it seemed to be difficult because of my lack of proficiency in searching keywords.

Note that 12 x 3 should be pronounced in the same way as shape e.g. 4x2 rectangle (rectangle with width = 4 and height = 2).

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    I think that should be 12mm x 3mm. Commented Jun 27, 2016 at 18:43
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    In my (SE UK) vernacular, I'd normally enunciate the x as by (same vowel as in high), but for more common dimensions such as 2 by 4 (inches), I'd normally reduce/shorten the vowel sound to that of, say, bit. That reduced enunciation explains many written instances of four be two Commented Jun 27, 2016 at 18:46
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    Nobody prefers to any form. And I'm basically a scientist, and have never met the usage you say is preferred. There are no Google hits for "2 by 1 square inches", "2 by 1 square centimetres", or "2 by 1 square imillimetres", and I suspect there won't be any if we substitute cm^2 etc. I'll ask the ex-coordinator of science teaching in our region next time I see him. Commented Jun 27, 2016 at 18:57
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    I think EdwinAshworth is saying that '36 mm^2' makes sense when describing an area, and '12mm x 3mm' makes sense when describing a shape, but the partially complete '12 x 3 mm^2' looks odd; even though (12x3)mm^2 = 12x(3mm^2).
    – AmI
    Commented Jun 27, 2016 at 20:17
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    You are confusing two ideas. For lengths, the 'x' or 'by' construction is commonly used (eg by joiners) to specify the relevant dimensions (eg 6 foot of 2" by 3", usually shortened to 6 foot of 2-bi-3). Scientists would say 36 mm^2. rather than 12 x 3 mm^2. If this is being written as a part of a calculation, 'x' reads as 'times'. Commented Jun 27, 2016 at 20:18

2 Answers 2


'by' as in 12 by 3 square millimeters

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    Or 12 by 3 millimeters squared. Either is acceptable.
    – Catija
    Commented Jun 27, 2016 at 20:53
  • @Catija I agree, either pronunciation of the units is acceptable.
    – Underminer
    Commented Jun 27, 2016 at 20:57

If it is describing the size of a single rectangular shape, then by is the correct pronunciation.

If it is describing a number of squares, then you can leave it silent.

12 3 millimeter squares.

If it is a scalar multiplied to a square unit in a mathematical calculation, then times can be used.

12 times 3 mm2

  • 1
    The answer was authored before the OP added the additional note.
    – jxh
    Commented Jun 28, 2016 at 0:55

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