2D takeoff
A 2D takeoff uses the plan sheets: floor plans, elevations, sections, details and schedules. The estimator counts and traces on each sheet. The estimator reads heights from elevations and sections, because a plan view does not show them.
BIM takeoff
A BIM model holds the building as objects: walls, doors, ducts and equipment. Each object carries data, such as its type and its size. Software can list the objects and total them without tracing. A door count comes from the door objects, not from clicks on a plan.
Side by side
- Source. 2D uses sheets. BIM uses the model file.
- Work. 2D needs counting and tracing. BIM needs filtering and checking.
- Access. Every bidder gets the sheets. Many bidders never get the model.
- Detail. Sheets show what the design team chose to draw. A model shows what the design team chose to model.
Limits of a model takeoff
- A model is only as complete as the modeler made it.
- Small items are often not modeled: blocking, anchors, accessories, wall pads.
- The model can be newer or older than the issued sheets.
- Object data can be wrong. A door can carry the wrong type mark.
Which one governs
Read the bid documents. On many projects the drawings and the specification are the contract documents, and the model is for reference. Do not assume. If the model and the sheets disagree, ask the architect in writing before you bid.
Most specialty contractors bid from the Project Manual and the PDF sheets. Takeoff Tool works the same way. It reads the Project Manual and the plan sheets, not the model.
AI and takeoff software · Updated 11 Nov 2026