Irish measure

This article is about early modern units. For pre-modern units, see Old Irish units of measurement.

Milestone on Mountbellew Bridge, originally erected near by c.1760. Distances are given in Irish miles to: Dublin (79); Athlone (20) Ballyforan (9) Ballinasloe (2); Galway (23) Tuam (12) Dunmore (2)
Detail of John Rocque's 1794 map of Ireland showing scales of English and Irish miles
Milestone on the N2 road reading: Slane 5, Carrickmacross 21 and Collon 9 (Irish) miles. In modern statute miles this would be 6+1⁄3, 30+3⁄4 and 11+1⁄2 miles respectively.
Milestone in Athlone, indicating a distance of 60 Irish miles to Dublin. This is equivalent to 76 statute miles or 122 kilometres.
Milestone at Ballycarrane, stating that it is 8 Irish miles (16 km) to Rathkeale and 6 Irish miles (12 km) to Limerick.

Irish measure or plantation measure was a system of units of land measurement used in Ireland from the 16th century plantations until the 19th century, with residual use into the 20th century. The units were based on "English measure" but used a linear perch measuring 7 yards (6.4 m) as opposed to the English rod of 5.5 yards (5.0 m). Thus, linear units such as the furlong and mile, which were defined in terms of perches, were longer by a factor of 14:11 (~27% more) in Irish measure, while units of area, such as the rood or acre, were larger by 196:121 (~62% more). The Weights and Measures Act 1824 (5 Geo. 4. c. 74) mandated the use throughout the British Empire of "Imperial measure", also called "statute measure", based on English measure. Imperial measure soon replaced Irish measure in the use of the Dublin Castle administration, but Irish measure persisted in local government, and longer still in private use.