What it means
An estimator reads plans for a new building and measures concrete volume, wall area and fixture counts, and those quantities feed a cost estimate after unit rates, waste and other costs are considered. RICS NRM 2 provides detailed measurement rules for building work and bill-of-quantities preparation, but its rules are a particular framework, so a project should state the measurement basis it uses.
Autodesk describes taking off linear, area and count quantities from 2D drawings and 3D models, and software can speed measurement but cannot fix an incorrect model or missing scope. Confirm document versions, because a superseded drawing can yield precise-looking but wrong quantities, and record the revision and date for each measured source.
Define the scope too: siteworks, temporary works, finishes and mechanical and electrical systems may or may not be included, and a take-off for one trade is not the entire project. Choose units that suit each item, such as cubic metres for concrete, linear metres for pipe and counted numbers for doors, since mixing units makes pricing and comparison unreliable.
Apply measurement rules consistently, because openings, overlaps and deductions can be treated differently by standard or contract, so state assumptions rather than silently switching methods. Check scale, since a drawing printed at the wrong scale or a model with wrong units can multiply every result, and verify a known dimension before broad measurement.
Read specifications with plans, because a wall length alone does not reveal material, thickness, fire rating or finish, and those attributes affect item definition and cost. Avoid double counting, since an item shown on a plan and schedule should appear once under the chosen breakdown, and cross-check counts against room or floor totals.
Identify missing information, because an unresolved facade design may require an assumption or provisional allowance, not fabricated certainty, and gaps should be marked for the design team in an assumption log naming who must confirm each one. Account for waste separately, since net measured tile area and purchasable tile quantity can differ due to cuts and breakage, and the estimating method should show the added factor.
An illustrative purchase quantity is net area times (1 + assumed waste), so a 100-square-metre floor at an illustrative 10% allowance suggests 110 square metres to purchase, before pack rounding; the factor is project-specific. A take-off says how much work or material is measured but does not directly say crew hours, because productivity rates and site complexity drive labour estimates.
Link each measured line to an estimate item, unit rate and scope note, since a large unpriced take-off is not a complete tender. Reconcile model and site, because existing buildings may have hidden conditions and site surveys can change dimensions or quantities, subject to the contract's adjustment rules.
Use review checks, such as another estimator sampling major quantities or comparing ratios with similar projects, track changes by showing the quantity delta and source revision without overwriting the baseline, and give major cost drivers such as structure, facade or groundworks a closer check, because a small percentage error on a large package can overwhelm many accurate small items. Keep measurement and ordering distinct, since supplier pack sizes, minimum orders and lead times may increase purchased quantity beyond the measured need, while for owners the take-off makes the physical scope measurable and its quality depends on current design information, consistent rules and visible assumptions.
In practice
Real-world examples.
Example
An estimator measures 100 square metres of tile area from current floor plans and records the drawing revision. The net area is later increased by an allowance for cuts and breakage. The purchase quantity is rounded up to whole packs.
Example
A door schedule supplies a count that is reconciled with room drawings. The estimator finds two doors on the schedule that do not appear on the plan. The query goes to the design team before pricing.
Example
A revised facade drawing changes the measured window quantity. The estimator records the quantity change and the revision that caused it, then updates the estimate while keeping the baseline history. The client sees the cost effect of the revision.
Formula
Calculation
Illustrative purchase allowance = net measured area x (1 + assumed waste factor), then rounded up to whole packs. The 10% factor below is not universal.
Worked example. A fictional floor measures 100 m2 net, and tiles are sold in packs covering 4 m2.
- Allowance = 100 x 1.10 = 110 m2.
- Packs = 110 / 4 = 27.5, rounded up to 28 packs, which is 28 x 4 = 112 m2 purchased.Case study
Seen in the real world.
This entirely fictional example follows Cedar Build. It priced an old drawing revision and missed ten doors added later. Its estimator introduced revision IDs and a second-person check of large quantity changes. The final purchase plan also accounted for supplier pack sizes.
The case does not imply take-off quantities alone establish contract price. On its next project, the second-person check caught a basement wall extension that would otherwise have been left unpriced. The estimator logged the assumption and sent a query to the design team. The fictional episode shows how a simple check protects the estimate.
Watch out
Common mistakes.
- Measuring from an outdated drawing without recording its revision.
- Treating a measured quantity as a finished price or procurement quantity.
- Mixing measurement rules or double counting items shown in several views.
Questions
People also ask.
What is a quantity take-off?
A measured list of construction quantities for a defined scope.
Is a quantity take-off a complete cost estimate?
No. Unit rates, labour, waste, overhead and other costs must be added.
What might change measured quantities?
Design revisions, site findings, assumptions and measurement rules can change it.
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