How to measure baseboard and trim without coming up short
Base is the easiest takeoff in the house to get roughly right and one of the easiest to get exactly wrong, because of one subtraction that should not happen.
The rule, in one line
That is the whole of it, and the window is where people go wrong. A window is a hole in the wall face and it is not a hole in the base run, because there is wall below it. Subtract windows and every room in the house comes up short.
What else eats the run
- A hearth or a fireplace surround, if the base dies into it.
- Full-height cabinets and built-ins — base stops at them.
- A staircase, where the base becomes skirting and is a different item.
- Open closets, which usually ADD run rather than remove it.
Closets are the reliable surprise. A pair of reach-in closets can add fifteen or twenty feet of base to a bedroom, and they are not part of the room you paced out.
Casing is a count, not a length
Casing goes round openings, so it is worked out per opening and then added up. A standard door cased both sides takes roughly twice its perimeter less the sill:
| Opening | Casing per side | Both sides |
|---|---|---|
| 3 ft × 6 ft 8 in door | ≈ 17 ft | ≈ 34 ft |
| Window, 3 ft × 5 ft, cased four sides | ≈ 16 ft | usually one side only |
| 5 ft cased opening | ≈ 21 ft | ≈ 42 ft |
Count the openings first, decide which are cased on one side or both, then multiply. Trying to hold that in your head while walking the house is how a door gets missed.
Buying it in lengths
Trim comes in fixed lengths and you cannot join it invisibly on a short wall, so the useful number is not total linear feet — it is the list of individual wall runs. Nine feet of base on an eleven-foot wall is one sixteen-foot stick, not nine feet of stock.
A takeoff that gives you a single total is fine for pricing and useless for ordering. Keep the wall-by-wall list.
Where the perimeter comes from
Base is perimeter arithmetic, so it is only ever as good as the perimeter. That is the number a phone scan gives you quickly and a tape gives you properly — and Trueline keeps the two apart, wall by wall, so a base figure standing on a scan says so.
Working round a staircase
Where base meets a stair it usually becomes skirting, cut on the rake, and that is a different item at a different labour rate. Measure it separately and price it separately — a run of raked skirting priced as straight base is one of the reliable ways to lose money on a hallway.
The same is true of returns at the bottom of a stringer, and of any base that dies into a newel post. They are counted, not measured.
Crown, and why it is not base upside down
Crown runs the perimeter at the ceiling, so it does not lose the doors — a door does not reach the ceiling. It runs the full perimeter, and it gains anything base loses to a cabinet, because the uppers stop below the crown line unless somebody has run it to the cabinet tops.
Mitres are where crown costs money. Inside and outside corners are counted, not measured, and an eight-corner room takes far longer than a four-corner room of the same perimeter.
Waste, and the offcut you can use
Base offcuts are usable in a way flooring offcuts often are not: a short piece goes in a closet, behind a door swing, or on a short return. So the useful discipline is to list the runs longest first, buy for the long ones, and let the shorts come out of what is left.
That only works if you kept the wall-by-wall list. A single total in linear feet cannot tell you whether you need six sixteen-foot sticks or twelve eight-foot ones.
Free download: Room takeoff sheet — a blank PDF to print, generated by the same code that produces the app’s own documents. All the templates.
Questions people ask
- Do you subtract windows when measuring baseboard?
- No. The base runs under a window because there is wall below it. Only doors and cased openings come out of the perimeter.
- How do you calculate linear feet of baseboard?
- Add the wall lengths to get the perimeter, subtract the width of every door and cased opening, and add any closet walls that are getting base. Keep the wall-by-wall list for ordering — the total alone will not tell you what lengths to buy.
- How much casing does a door take?
- Roughly the perimeter of the opening less the floor side, which is about 17 feet on a standard 3 ft × 6 ft 8 in door. Double it if the door is cased on both sides.
- Do you deduct doors from crown moulding?
- No. Crown runs at the ceiling and a door does not reach it, so crown takes the full perimeter. It is base that loses the doors, and base that stops at cabinets while crown carries on above them.
- How do you price raked skirting on a staircase?
- Separately, and at a higher labour rate than straight base. Every cut is an angle, the returns at the bottom are their own item, and pricing it as ordinary base is a common way to lose money on a hallway.
Where this fits with Trueline
Trueline is an iPhone app that measures a room, takes it off, prices it from your own rate book and turns it into a proposal — with every length carrying whether it was scanned, drawn or measured, right onto the document a client reads. See how it works, or take the free templates and use them with whatever you already have.