How to read a line's arithmetic
What the derivation on a takeoff line says, step by step, with an example.
Every takeoff line can show its derivation: the steps that turned what was read from the drawings into the quantity on the line. Nothing is hidden, so you can check it the way you would check a colleague's count.
The steps
A derivation lists one step per element, then the totals.
- Each wall or opening behind the line, with the rule applied to it: for example, one stud per 16 inches plus one to close the wall.
- Additions and subtractions: extra studs at corners, studs removed inside an opening, king and jack studs beside it.
- The net quantity: what the drawings require.
- The order quantity: the net quantity with waste from your estimating standards, rounded up to whole pieces.
An example
A 32 foot wall with 2 corners and one 3 foot door reads like this:
- W1 studs: ceil(32 x 12 / 16) + 1 = 25
- Corners: 2 x 3 = 6
- D1 inside opening: -2
- D1 king and jack: 4
- Net Quantity: 33
- Order Quantity: ceil(33 x 1.05) = 35
"ceil" means rounded up to the next whole number.
When a number looks wrong
Check the elements first. If a wall was read at the wrong height or length, correct it and the whole takeoff recomputes. See "Correcting a wall height and recomputing".
If a rule is not how your yard frames, change it in Settings, then Estimating standards. New standards apply to new takeoffs, which are charged as usual. A takeoff that has been released keeps the standards it was made with.