Wikipedia: ISO 216

NameH (mm)W (mm)
A01189841
A1841594
A2594420
A3420297
A4297210
A5210148
A6148105
A710574
A87452

Any consecutive pair of numbers from the following number series is a paper size in the A series, with the A4 pair bolded and underlined:

2378 1682 1189 841 594 420 297 210 148 105 74 52 37 26

And the same for the B series, with the B4 pair bolded and underlined:

1414 1000 707 500 353 250 176 125 88 62 44 31

And the same for the C series, with the C4 pair bolded and underlined:

1297 917 648 458 324 229 162 114 81 57 40 28