How to do a material takeoff
Measure, deduct openings, add waste, then round up to what the supplier actually sells. The last step is the one that gets skipped.
The short answer
A takeoff converts drawings into quantities you can price and order. Work in the order of measure, deduct openings, apply a waste factor, then round up to the pack or sheet size the supplier sells, because the last step frequently adds more than the waste factor did.
The formula
wall area = perimeter x height
net area = wall area - openings
with waste = net area x (1 + waste factor)
units to buy = ceiling(with waste / coverage per unit)
Waste factors are not padding. Cutting loss, breakage and offcuts are physical, and 10% for paint and boards with 8% for flooring are ordinary starting points that go up with complex layouts.
Worked example
A room 4.2m by 3.6m with 2.4m walls, one door of 1.8 square metres and one window of 2.4:
wall area = 2 x (4.2 + 3.6) x 2.4 = 37.44 m²
net of openings = 37.44 - 4.2 = 33.24 m²
paint, 2 coats at 10 m²/L, +10% waste = 7.31 L → 3 x 2.5L tins
plasterboard 1.2 x 2.4 = 2.88 m² each
33.24 x 1.10 / 2.88 = 12.7 → 13 sheets
flooring 4.2 x 3.6 = 15.12 m², +8% = 16.33
packs of 2.2 m² → 7.4 → 8 packs
Every one of the three rounds up to a whole unit, and on flooring the rounding adds 4.3% on top of the waste factor. Ordering the calculated quantity rather than the purchasable one is how a job runs out on a Friday.
When to deduct an opening and when not to
For paint, deduct anything over about half a square metre. For plasterboard, deduct large openings only, because a sheet cut around a small window still consumes most of a sheet.
This is the most common source of disagreement between two takeoffs of the same room, and both can be defensible. What matters is being consistent, so your own historical figures stay comparable.
Waste is not one number
It scales with complexity rather than with area. A rectangular room with two openings wastes very little; the same area broken into alcoves, angles and a stairwell wastes a great deal more.
Pattern-matched materials are their own case. Wallpaper with a large repeat, or tile laid diagonally, can waste 15% to 20%, and using a general 10% on either produces a shortfall rather than a saving.
Long thin rooms waste more flooring than square ones of the same area, because more of the cut lengths become unusable offcuts.
Recording what you actually used
The takeoff is an estimate; the delivery notes are the truth. Comparing them after each job builds waste factors specific to your work and your team, which beats any published figure within about five jobs.
It also catches the quiet problems: consistent over-ordering that is being absorbed as van stock, or a material that always runs short because the coverage on the tin assumes a surface yours never is.
What this leaves out
- Coverage rates are illustrative. Paint coverage in particular varies substantially with surface porosity and colour change.
- Excludes fixings, adhesives and sundries, which are usually estimated as a percentage rather than taken off.
- Assumes standard sheet and pack sizes. These differ by country and by supplier, and the rounding depends entirely on them.
Common questions
- What waste factor should I use?
- Ten percent for paint and boards, eight for simple flooring, fifteen to twenty for patterned or diagonally laid materials. Then replace all of them with your own figures once you have tracked a few jobs.
- Should I take off from drawings or from site measurements?
- Site measurements whenever the building exists. Drawings are frequently out by enough to matter, especially in older properties, and a takeoff from an inaccurate drawing is confidently wrong.
- How do I handle materials sold in odd sizes?
- Round up to the purchasable unit and record the rounding separately from the waste factor. Keeping them apart is what lets you see that the rounding, not the waste, is what added the extra pack.
Spreadsheets that do this
The formulas above, already built and checked — so you fill in your numbers rather than the arithmetic.
Related guides
Last reviewed 22 August 2026