Latin, acra.

Fiscal acres must be distinguished from real acres on the ground. The fiscal acre was an artificial unit, not a measurement of area. As part of the system of assessment, a fiscal acre was normally 1/120th of a hide, or 1/30th of a virgate, as many Domesday entries demonstrate. J.H. Round long ago provided illustrations of this equation in the relationship of hides, virgates and acres, mainly from circuit 3 and especially from Cambridgeshire, where many entries record acres and where the Cambridge Inquisitionprovides totals for the hidage of each vill as well as each manor, giving more confidence in the arithmetical results.

The four entries for Isleham provides an example of an equation involving acres:

Entry Hides Virgates Acres

1,3 6 0 40

4,1 1.5 0 20

14,72 0 0 40

28,1 1.5 0 20

The entries total 9 hides and 120 acres, so if the equation 1 hide = 120 acres holds true, then the vill of Isleham was assessed at 10 hides, or two 5-hide units. In many counties, such units are common.

However, fiscal hides of 40, 48, and 60 have been identified in some counties, and in others no consistent relationship between hides and acres can be established. Although the fiscal acre normally bore some relationship to the size of an acre in the fields, this could be varied by royal grant or immunity, the nature of the soils, or according to local custom.

On the artificiality of the system in some areas, see J.H. Round, Feudal England (1895); R.A. Leaver, Five hides in ten counties', Economic History Review, second series, vol. 41 (1988), pages 525-42; and John J.N. Palmer, 'The Domesday manor', Domesday studies, edited by J.C. Holt (1987), pages 139-54; and for fiscal hides of various sizes, see F.W. Maitland, Domesday Book and beyond (1987); James Tait, 'Large hides and small hides', English Historical Review, vol. 17 (1902), pages 280-82; and R.R. Darlington, 'Introduction to the Wiltshire Domesday', Victoria History of the county of Wiltshire, vol. 2, edited by R.B. Pugh and E. Crittall (1955), pages 42-177.