The paper length is not relevant since the chart flows from one page to the next.
Mobile
in.
mm
Portrait
2.75
70
For smart phones, not for printing
Landscape
5.5
140
For smart phones, not for printing
USA & Canada
in.
mm
Letter Portrait
8.5
216
Also Legal Portrait
Letter Landscape
11
279
Legal Landscape
14
356
Also Ledger Portrait
Ledger Landscape
17
432
International
in.
mm
A5 Portrait
5.82
148
A4 Portrait
8.25
210
Also A5 Landscape
A4 Landscape
11.71
297
Also A3 Landscape
A3 Landscape
16.54
420
The Text+ programs assume that the right and left margins are each about 25mm (1/2 inch) wide.
On the Format for Printing page, differences in page margins can be accommodated by the "fudge factor":
Legend:
Father: Hugh Gifford (of Yester, East Lothian, Scotland - Between 1356 and 1366)
    :   └─Margaret Hay (Abt 1400 - Aft 22 Apr 1484)
    :    William Douglas (24 Feb 1398 Tantallon Castle, East Lothian, Scotland - Oct 1437)
    :    (m. Abt 1414 Yester Castle, Gifford, East Lothian, Scotland)
    :       ├─George Douglas ( - 12 Mar 1463) =>
    :       │ + Isabel Sibbald ( - Between 1 Dec 1500 and Feb 1503)(m. Bef 1446)
    :       └─Helen Douglas (Abt 1436 - Aft 20 Nov 1486) =>
    :        + William Graham (Abt 1426 - Abt 1471)(m. Bef 1460)