381mm (H) X 254mm (W)
foolscap is a legal or "long" paper
What is the standard-size large envelope?
The standard size business envelope is the number ten. The number ten envelope is open sided with a commercial style flap.
An envelope can never be too large for itself.
3 1/2" x 5" (inches) is the smallest legal mailing size for an envelope in the US.
foolscape paper
Depends on the type and size of the page and envelope.
The size of the envelope and forms both matters.
4" by 9"
The number 10 envelope is the most widely used envelope these days. The size of the number 10 evelope is 4 1/8 by 9 1/2 inches. This common size is used by businesses for doing mass mailings.
It depends on tne weight of the envelope not the size.