The Leeson Generation Grid is used to help you locate the individual you are looking for. Where given, the letter indicates the probable generation of the individual.
| Generation letter | Year of birth |
| H | 1590-1619 |
| I | 1620-1649 |
| J | 1650-1679 |
| K | 1680-1709 |
| L | 1710-1739 |
| M | 1740-1769 |
| N | 1770-1799 |
| O | 1800-1829 |
| P | 1830-1859 |
| Q | 1860-1889 |
| R | 1890-1919 |
| S | 1920-1949 |
| T | 1950-1979 |
| U | 1980-2009 |
Where a double letter is given, this should be interpreted as follows:
| A 'Leeson' of | MM | indicates born | 1740-1769 |
| MN | 1740-1799 | ||
| MO | 1740-1829 |