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Accuracy Most users have their "standard" ways of checking the accuracy of a rule. For some scales this is easy; for example 3 x 3 equals 9 and sin 30° equals 0.5. For other scales, tan and CF (p shifted) this is not as easy as there are no simple comparisons. The following table gives details of marks which will line up for the other scales and the precision of the alignment. As can be seen, in all cases the precision is much better than 1 : 27 000. It should be noted that the alignments for log-log scales do not work for all rules as the figures assume that the rule are based on natural (Naperian) logarithms. |
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| Scale | Description | Value | C/D scale | Precision |
| Sin | Sine | 30° | 0.5 | Exact |
| Tan1 | Tangent < 45° | 19.90° | 0.362 | 1 : 71 000 |
| Tan2 | 45° < tangent < 85° | 82.20° | 7.30 | 1 : 42 000 |
| Logs | log base 10 | 3.02 | .48 | 1 : 77 000 |
| CF | p shifted | 7.10 | 2.26 | Almost exact |
| W | Ö10 shifted | 7.40 | 2.34 | 1 : 27 000 |
| P | Pythagorean Ö(1- x2) | 0.6 | 0.8 | Exact |
| LL3 | log-log, 2.7 to 5 x 105 (log base e) | 8.50 | 2.14 | 1 : 32 000 |
| LL2 | log-log, 1.1 to 2.7 (log base e) | 1.60 | 0.470 | 1 : 125 000 |
| LL1 | log-log, 1.01 to 1.1 (log base e) | 1.0142 | 0.0141 | 1 : 110 000 |