Quantities and cost (5D)
Can the estimator trust quantities from the model?
Model quantities are fast and update with the design, but only if elements are classified, measured the way cost rules expect, and free of duplicates. Here's what estimators need from your model.
Understand
What it is, in plain language
- Pedia · WorkflowsQuantity take-off (QTO)Measuring quantities — counts, lengths, areas, volumes — from a model instead of drawings, and what has to be true of the model for the numbers to be trusted.
- Pedia · WorkflowsModel-based estimating (5D)Using quantities from the model, mapped to a cost structure and priced with rates, to produce and update estimates, and knowing which parts of the estimate the model can't provide.
- Pedia · StandardsMeasurement and cost classification standards (NRM, ICMS, UniFormat, MasterFormat)The rules that say how construction work is grouped and measured for cost, and why a model that ignores them gives quantities an estimator can't use.
- Pedia · Workflows4D and 5D BIM (time and cost)Linking model elements to the construction programme (4D) and to quantities and cost (5D), and what each is useful for.
- Pedia · ClassificationUniclassThe UK’s unified classification system for the built environment — tables for complexes, entities, spaces, elements, systems, products and more, with codes like Ss_25_10_30.
- Pedia · SoftwareProperty sets (Psets) and quantity setsHow IFC groups element information into named sets of properties and quantities, the standard Pset_ and Qto_ sets, and custom sets.
Learn
Short lessons with a quick check
- Lesson · 4 min · quizQuantities you can trustModel quantities are fast and update with the design, but estimators only use them if elements are classified, measured the way cost rules expect, and counted once.
- Lesson · 4 min · quizFrom quantities to an estimate (5D)Quantities become an estimate through mapping and rates, and the model's real value shows when the design changes. What 5D can and can't do.
Do
Tools that export Excel, PDF and Word
- Tool · Excel · PDF · WordQuantity Take-off and 5DUse it to price a model, to see where the money sits in the building, and to explain what a design change costs and where.
- Tool · Excel · PDF · WordIFC to Excel SchedulesUse it when you need quantities, a door or equipment schedule, or a property review from an IFC model in Excel.
- Tool · Excel · PDF · WordIFC InspectorUse it when you receive an IFC file, before you federate or share it.
- Tool · Excel · PDF · WordModel CompareUse it when a new model version arrives and you need to know what changed since last week.
The process, at a glance
- 1Classify
Every measured element carries a classification code
Output: Classified model
Gate: No unclassified elements in measured categories - 2Extract
Quantities per type: count, length, area, volume
Output: Quantity table
Gate: Duplicates between models removed - 3Map
Types to cost items by classification
Output: Measured items
Gate: Every type mapped, net and gross stated - 4Price
Rates per cost item
Output: Priced items
Gate: Rates current, source stated - 5CompleteMandatory
Add what the model can’t give: preliminaries, risk, unmodelled items
Output: Estimate
Gate: Report says what came from the model and what didn’t
Each step has an output and a check. The estimate is only as good as the weakest gate.
Common mistakes
What goes wrong most often on real projects.
- Pricing schedule totals without checking scope and duplicates.
- Mapping types to cost items by name instead of by classification.
- Mixing net and gross quantities.
- Presenting a model-based estimate as complete when it only covers modelled work.
Is it in place on your project?
Tick what is done — it counts towards the checkpoint on your learning path.