what means demy size?

[Shail98]

which size is exactly same as demy size? a3??

[Peter Spier]

can you provide some more context, please?

[Robert at ID-Tasker]

@Shail98

From Google:

Demy Paper Size Dimensions

44.5 x 57.2 cm

445 x 572 mm

17.5 x 22.5 in

0.4 x 0.6 m

1261.6 x 1621.6 pt

105.1 x 135.1 pc

5256 x  6756 px

[Derek Cross]

Demy, like other old standard sizes such as Crown have been replaced (mostly) in Europe by the DIN A B and C system.

From memory Demy 8vo was a popular book size of TPS 81⁄2 x 51⁄2 inches.

[James Gifford—NitroPress]

There are a lot of classic measurement systems across modern history, but paper and its endless systems of weight, size, finish etc. remains in a class of its own. 🙂

[Derek Cross]

Interestingly, commercial poster sites in the UK are still based on the Crown paper size of 15 x 20".
They are described as "sheets" 1 sheet being Double crown: 20 x 30"; 2 sheet Quad crown 30 x40" and so on.

[James Gifford—NitroPress]

Fine stationery, mostly for wedding sets these days, still uses the old size and finish designations. But all good; something has to justify the inflated pricing. 🙂