Ireland
units of length

The Irish units of length show the influence of the Celtic (cf. Scottish, Welsh, Breton), Norse, Roman (through the Church) and English systems.

Old Irish

Units mentioned in the Brehon Laws, probably written in the 7th century.

forrach

fertaig

12

deisceim

2

24

ceim

2

4

48

trogid

3

6

12

144

dorn

2

6

12

24

288

bas

3

9

18

36

432

ordlach

4

6

12

36

72

144

1728

grain

3

12

18

144

432

864

1728

20736

Taking the ordlach as = 1 inch 

1/3
in

1
in

4
in

6
in

1
ft

3
ft

6
ft

12
ft

48
yd

 

The inntrit and lait, falling somewhere between the deisceim and the forrach, are not included in the chart for the reason discussed in the entry on the tir cumaile.

The later system

The following charts are very incomplete. Any information from readers would be most welcome. The first chart takes 1 Erse pole = 105/8 bandles, that is 13 1/8. The second assumes 1 Erse pole = 10½ bandles.

Erse mile

Erse furlong

8

forrach

10

80

Erse  pole

3 17/21

38

304

fertach

2.625

10

100

800

piece

1 2/3

4.375

16 2/3

166 2/3

1333 1/3

ceim

2 2/5

4

10 ½

40

400

3200

bandle

1 1/4

3

5

13 1/8

50

500

4000

troigid

1 3/5

2

4.8

8

21

80

800

6400

bas

ordlach

20

24

30

72

120

315

120

1200

9600

1
inch


in

20
inches

2
ft

30
inches

6
ft

10
ft

26 1/4
ft

100
ft

1000
ft

8000
ft

Erse mile

Erse furlong

8

forrach

4 2/3

37 1/3

Erse  pole

8 4/7

40

320

fertach

1 2/5

12

56

448

piece

30

140

1120

ceim

2 2/5

6

8 2/5

40

186 2/3

1493 1/3

bandle

3

7.5

10½

90

420

3360

troigid

1 3/5

2

4.8

12

21

180

840

6720

bas

6

18

45

63

540

2520

20,160

ordlach

4

15

24

30

72

180

252

2160

10,080

80,640

1
inch

4
in

15
in

24
in

30
in

6
ft

15
ft

21
ft

180
ft

840
ft

6720
ft

?6721

home | units index | search |  to email Sizes drawing of envelope |  acknowledgements | 
help | privacy | terms of use