# The Measuring Instruments Regulations 2016, Paragraph 2: MPEs


The MPE, positive or negative in mm, between two non-consecutive scale marks is (a + bL), where:
— L is the value of the length rounded up to the next whole metre; and
— a and b are given in Table 1 below.
When a terminal interval is bounded by a surface, the MPE for any distance beginning at this point is increased by the value c given in Table 1.
Table 1
Accuracy Class
a(mm)
b
c(mm)
I
0.1
0.1
0.1
II
0.3
0.2
0.2
III
0.6
0.4
0.3
The MPE for the length between consecutive scale marks, and the maximum permissible difference between two consecutive intervals, are given in Table 2 below.
Table 2
Length i of the interval
MPE or difference in millimetres according to accuracy class
I
II
III
i ≤ 1 mm
0.1
0.2
0.3
1 mm < i ≤ 1 cm
0.2
0.4
0.6
Where a rule is of the folding type, the jointing shall be such as not to cause any errors, supplementary to those above, exceeding: 0.3 mm for Class II, and 0.5 mm for Class III.

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Source: https://www.legislation.gov.uk/uksi/2016/1153/schedule/1I/part/chapter/1/paragraph/2 (the official version)
Page: https://openlegislation.uk/measuring-instruments-regulations-2016/schedule-1I/part/chapter-1/paragraph-2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.