Construction estimating: material quantities, waste factors and order units
For site supervisors, trainee estimators, tradespeople and purchasing staff who work out how much material to order from drawings. You should be comfortable with percentages and unit conversion (the b3-business-numeracy course covers them) and able to read dimensions from a plan. You calculate net quantities for areas, volumes and lengths, apply waste factors that suit the material, convert to the units suppliers sell (cubic yards, sheets, boxes, pieces), check a takeoff for the errors that cause short or excess deliveries, and document the basis so allowances improve with each job. Examples use US customary units with exact metric conversions. Waste allowances shown are fictional; your company's records and supplier units govern.
- Level
- Beginner
- Length
- About 95 minutes
- Contents
- 5 lessons · final exam
- Status
- Published · updated 10 Oct 2026
Skills you'll practise
- Calculate net material quantities from drawing dimensions for areas, volumes and lengths
- Apply a waste factor to a net quantity and choose an allowance that suits the material and the job
- Convert quantities into order units such as cubic yards, sheets, boxes and pieces, rounding up only at the end
- Check a material takeoff for errors such as missed openings, unit mix-ups and waste applied twice
- Document the estimate's basis and compare actual waste with the allowance to update it
Course outline
- 1.Calculating net material quantities from drawing dimensionsLesson · 20 min
- 2.Applying a waste factor that suits the material and the jobLesson · 18 min
- 3.Converting quantities into order units and rounding up only at the endLesson · 18 min
- 4.Checking a material takeoff for errorsLesson · 17 min
- 5.Documenting the estimate's basis and comparing actual waste with the allowanceLesson · 12 min
- 6.Construction estimating: material quantities, waste factors and order units: knowledge checkKnowledge check · 14 questions
- 7.Construction estimating: material quantities, waste factors and order units: practical exerciseKnowledge check · 1 question
- 8.Final exam10 questions · passing it completes the course, so people who already know the material can test out
Sources it draws on
The lessons and questions are written from these references, so learners can go back to the original.
- NIST Guide to the SI (SP 811), Appendix B.9: Factors for units listed by kind of quantity
- NIST: Unit Conversion
- USDA Forest Products Laboratory, Wood Handbook (FPL-GTR-282, 2021), Chapter 6: Commercial Lumber, Round Timbers, and Ties
- US EPA: Sustainable Management of Construction and Demolition Materials
- US GAO: Cost Estimating and Assessment Guide (GAO-20-195G), product page
See it with your own jobs and topics
Tell us about your team and we'll walk you through setup, from choosing jobs to your first skills check.