Measurement Guides
Metric vs Imperial Measurements for CNC and Woodworking
Published · Updated
Switching a drawing from millimeters to inches should not resize it. The more difficult distinction is between a nominal stock label, a rounded display and an exact input. They can look similar while describing different production dimensions.
Conversions are not interchangeable stock sizes
One inch is exactly 25.4 mm. Multiply inches by 25.4 to express the same physical length in millimeters; divide millimeters by 25.4 for inches. Choosing thickness by a rounded whole millimeter can change panel sizes.
| Input | Exact millimeters |
|---|---|
| 3/4 inch | 19.05 mm |
| 23/32 inch | 18.25625 mm |
| 1/64 inch | 0.396875 mm |
| 18 mm | 18 mm — not 3/4 inch |
Enter practical fractions
In inch mode, CutNavi accepts 3/4, 18 1/2, 18-1/2, decimals and explicit quote/in suffixes. A mixed 24 3/8 inches is exactly 619.125 mm. The visible in input suffix is UI text and need not be typed.
Malformed values such as 1/0 or 3//4 are rejected. For CSV, an inch quote inside a quoted cell must be doubled. Choose input units deliberately when unmarked numbers could mean either inches or millimeters.
Display resolution is not geometry precision
Fractional display rounds labels to a chosen 1/8, 1/16, 1/32 or 1/64 resolution. Decimal display is another representation; neither replaces the stored geometry with the rounded label.
CutNavi uses integer picometer canonical dimensions and precise millimeter storage for supported input. Common woodworking fractions through 1/64 inch survive revisions, optimizer transfer and persistence. Switching units creates no geometry revision and does not mark a saved design dirty.
Check units at the export boundary
Choose SVG/DXF and CSV output units explicitly. A 3/4-inch thickness can appear as 0.75 inches or 19.05 millimeters and describe the same geometry. Machine-readable CSV fields use decimal values with a unit, not rounded fractions.
A receiving CAD application may have its own import scaling setting. Check a known dimension after import before using a drawing. Unit support does not turn panel outlines into compensated toolpaths or certify a machine workflow.