Last updated 10 August 2026
As many as it takes for the converted band to fit inside the original. Three decimals of a millimeter is the usual working precision, four for a band tighter than about half a thousandth of an inch.
The test is not aesthetic. Convert, round inward, and check that the result is contained in the original band. If rounding inward at your chosen precision leaves nothing, or inverts the pair, you need another decimal place, and the tight case above is what that looks like.
Carrying more decimals than the process can hold is its own mistake in the other direction: a limit stated to five decimals of a millimeter claims a precision no shop-floor gauge will resolve, and invites an argument at inspection.
| Given | 0.4999 / 0.5001 in |
|---|---|
| Rounded to nearest, which is wrong | 12.697 / 12.703 mm |
| Rounded inward | 12.698 / 12.702 mm |
Open this case in the calculator, and change the numbers.
Computed by ctrlPlanner. ASME Y14.5, ISO 286.
This converts one value. ctrlPlanner holds both units on the same plan and applies the same inward rounding everywhere, so a whole print comes out in whichever unit the customer asked for.
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