DXF imports at the wrong size: measure before scaling

Measure a known feature in the source drawing and after import. The ratio tells you more than the overall appearance of the preview.

Check whether the error is uniform

Divide the intended length by the imported length. An intended 100 mm edge imported as 3.937 mm suggests an inch/millimetre interpretation problem, with a correction factor near 25.4. Measure a second feature in another direction. If the ratios differ, investigate transforms or the export geometry rather than applying one uniform scale.

Inspect units and export context

DXF unit metadata can be missing, ambiguous or interpreted differently by an importer. A missing units field in an export dialog does not prove that the DXF has no unit header. Also check whether the file came from a scaled drawing view, a transformed block or the intended model-space sketch. Ask the sender for the intended units and one reference dimension if neither is known.

Correct one cause and verify again

Use the intended unit interpretation on import when possible. DXF Medic offers a units override; use it only when you know the source units. Do not combine a unit correction with an unexplained manual scaling factor. Re-export a corrected file, reopen it in the destination tool and measure both reference features. Keep the original and record the correction so another operator does not apply it twice.