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DTM Tools workflow guide

Calculate cut and fill volumes
in AutoCAD

Compare existing and design terrain surfaces, or measure a stockpile against a fixed datum, with a reported cut, fill and net result plus a drawing-based colour map.

8 min readDTM ToolsSurface or datum modeUpdated June 12, 2026

Quick answer

Run DTM_Volume, choose Surface or Datum mode, select the existing surface, select the design surface or enter the reference elevation, and set the calculation grid. DTM Tools reports cut, fill and net volume and creates a colour map over the common area.

Surface mode is suited to existing-versus-design comparisons. Datum mode is suited to stockpiles, excavations or any single surface measured from a known flat level.

Video placeholder 08Existing versus design surface volume calculationShow both TINs, command prompts, colour map and final report label, 60 seconds.

Prepare trustworthy input surfaces

  • Confirm both surfaces use the same coordinate system and drawing units.
  • Check surface boundaries and remove triangles outside the intended calculation area.
  • Add important break-lines before calculating.
  • Use a deviation map to identify obvious terrain modelling errors.
  • Remember that the calculation uses only the common XY area of two surfaces.

Run the calculation

  1. Run DTM_Volume and choose Surface or Datum.
  2. Select the base surface, normally the existing terrain.
  3. Select the comparison surface, normally the design terrain, or type the datum elevation.
  4. Set the grid resolution used to sample the difference.
  5. Review the command-line totals, colour map and MTEXT report placed in the drawing.
Image placeholder 09Cut and fill map over a grading areaInclude surface boundary, red cut zones, blue fill zones and the report label.

Interpret cut, fill and net

DTM Tools calculates the height difference as comparison minus base:

  • Fill: the comparison or design surface is above the base surface.
  • Cut: the comparison or design surface is below the base surface.
  • Net = fill - cut: positive is net fill; negative is net cut.

Keep the order consistent: select existing ground as the base and design ground as the comparison if you want the standard construction interpretation.

Choose the calculation grid

Each grid cell contributes height difference multiplied by cell area. A finer grid follows small changes more closely but increases processing and may give a false sense of accuracy if the input scans or TINs are coarse.

Image placeholder 10Volume result at coarse and fine grid settingsShow identical boundaries with totals and sample-cell size for comparison.

Quality checks before issuing quantities

  • Confirm the reported area matches the expected project footprint.
  • Inspect unexpected isolated cut or fill cells.
  • Repeat with a second grid resolution and compare the totals.
  • Document the source survey dates, units and chosen resolution.
  • Use professional survey controls where contractual quantities are involved.
Create and verify the terrainGround extraction, TINs, break-lines and contoursExplore DTM ToolsFull feature list and installer