How to Convert the “Letter” Format in ISO216 A4

Letter Format (x,y):  215.9 x 279.4 mm  / ratio: 1.294

A4 (x,y):  210 x 297 mm  / ratio: 1.414

Proportion:  279.4 : 297 = Y : 100

             Y of "Letter" = 94.064 % (of 'Y' of A4)

New dimensions: 197.6 x 279.4 mm  (in A4 proportion)

Keeping the 'Y' Letter dimension, a reduction of 18.34 mm in 'X' Letter

would change the proportion of Letter into A4.

If x-symmetrical, the reduction (trim) must be -9.17 mm on each side.

How to Convert ISO216 A4 in “Letter” Format

A4 (x,y):  210 x 297 mm  / ratio: 1.414

Letter Format (x,y):  215.9 x 279.4 mm  / ratio: 1.294

Proportion:  210 : 215.9 = X : 100

             X of "A4" = 97.27 % (of 'X' of Letter)

New dimensions: 210 x 271.8 mm  (in Letter proportion)

Keeping the 'X' A4 dimension, a reduction of 25.2 mm in 'Y' A4

would change the proportion of A4 into Letter.

If y-symmetrical, the reduction (trim) must be -12.6 mm on top and bottom.

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