# Measure CAD Properties: Units, Dimensions and Valid Volume

Check units, separate envelope from local measurement, and preserve unavailable results in property exports.

Start with a known physical dimension. STEP solid properties use readable B-Rep geometry; STL/OBJ values are mesh approximations and assume millimetres. A shaded open surface can have area but no enclosed volume. Assembly totals require a defined scope; mass requires density.

## Work through the task

- [Measure STEP Files Online: Dimensions, Distances & Units](https://www.cadprops.com/guides/measure-step-file/index.md)
- [Do STL Files Have Units? How to Fix mm vs Inch Scale](https://www.cadprops.com/guides/stl-files-have-units/index.md)
- [STEP Inch Units: A Reproducible Dimension Check](https://www.cadprops.com/guides/step-inch-unit-check/index.md)
- [Open STEP Surface: Area Available, Volume Unavailable](https://www.cadprops.com/guides/step-open-surface-volume-case/index.md)
- [STEP Assembly Instances: Check Repeated-Part Totals](https://www.cadprops.com/guides/step-assembly-instance-properties-case/index.md)

## Use the matching tool

- [cad dimensions](https://www.cadprops.com/tools/cad-dimensions/index.md)
- [cad volume calculator](https://www.cadprops.com/tools/cad-volume-calculator/index.md)
- [cad surface area](https://www.cadprops.com/tools/cad-surface-area/index.md)

## Before accepting the result

Read warnings, confirm one known dimension and preserve units and scope. Files are processed on the server; see [privacy](https://www.cadprops.com/privacy/index.md) and [accuracy](https://www.cadprops.com/accuracy/index.md). [Browse all guides](https://www.cadprops.com/guides/index.md).

HTML page: https://www.cadprops.com/workflows/measure-cad-properties/