Inside or outside corner: where do you measure?
This is the mistake that costs a piece most often. A mitered end has two lengths, a long point and a short point. A measurement that does not say which one you mean cannot be cut.
Which dimension gets added or subtracted at a corner depends on how the piece sits. Look at it from above: the dimension you see from up there is the one that counts. Baseboard stands against the wall, so there it is the thickness, usually 1/2, 9/16 or 5/8 inch. A batten or trim lying flat shows its width instead, and then the width is what gets added or subtracted. On a 1-1/2 inch wide batten that is 1-1/2 inch, not 5/8.
| Situation | Where is the long point? | Length at the long point |
|---|---|---|
| Inside corner, mitered | At the back, against the wall | The wall length, corner to corner |
| Outside corner, mitered | At the front, wrapping the corner | Wall length plus the dimension seen from above |
| Inside corner, coped | The end is cut square | Wall length minus the dimension seen from above |
At a mitered inside corner the two backs meet exactly in the corner and the miter takes material off the front, so you simply measure the wall and that is your long point. At an outside corner it is the other way round: the fronts wrap past the corner while the backs stop at the wall, so the front is the long point and one dimension gets added per outside corner. With a coped joint the second piece lands against the face of the first, so there that dimension comes off.
That addition at an outside corner only holds at a true 90 degree corner. Where a wall runs off at an angle, a bay window at 135 degrees for instance, it is less: the amount added is the dimension times the tangent of half the change in direction, and at 135 degrees that is under half as much.
Rule of thumb. Measure the wall corner to corner and note which corners are inside and which are outside. Unsure about an outside corner? Cut it a little long and creep up on it. You can always take a hair off; you cannot put it back.
What angle do you set the saw to?
The standard answer is 45 degrees a side. That only holds if the corner is exactly 90 degrees, and it rarely is. So measure the corner first, with an angle finder or a digital protractor. But watch the conversion, because this is where it nearly always goes wrong: a miter saw and a miter box both count up from a square cut, not from the wall. The setting you dial in is half of how far the baseboard changes direction, so (180 minus the corner) divided by two.
At a 92 degree inside corner you set the saw to 44 degrees, not 46. At 88 degrees you set it to 46. That feels backwards: the wider the corner, the lower the setting. It is exactly why the mistake stays hidden, because at a true 90 degree corner both ways of figuring it happen to land on 45. The unmistakable check is an octagon: its inside corners are 135 degrees and every carpenter cuts one at 22.5, not at 67.5, which no miter saw will even reach.
Careful with a miter box. Its slots are fixed, usually 90 and 45 degrees and sometimes 22.5. You cannot cut 44 or 46 with it. If your corner is off square you need an adjustable miter saw, or you cope the joint, which works at any angle.
Watch how the baseboard sits on the saw too. On a miter saw you stand it up against the fence with its bottom edge on the table, exactly the way it will sit on the wall. Lay it flat and the miter will not match how it hangs. A circular saw or jigsaw will do the job as well, but then a guide is essential; see cutting straight with a circular saw.
Miter the outside corners, cope the inside ones
An outside corner is usually mitered: both pieces angled outward so they close up into a point around the corner. Cut it slightly long and fit it; the last fraction comes off easier than it goes back on.
An inside corner can be mitered too, but most finish carpenters cope it instead: the first piece runs square into the corner, and the end of the second piece is cut away to follow the profile of the first so it sits tight against its face. It is more work, but it stays closed when the corner is not square, which it almost never is, and it does not open up when the wood moves. It does change the length: the second piece lands against the face of the first, so it comes out shorter than the wall by the dimension seen from above.
With coped joints the order decides the result, and that is rarely mentioned. The wall you see first when you walk in gets a full-length piece with two square ends. The adjoining walls are coped against that. The joints then face away from you and you do not see them from the doorway. Work round the room in one direction after that, so every piece lands against the one before it.
Which way does the miter go?
In practice this costs more material than a bad measurement. You measure carefully, you set the saw right, and then you cut the miter the wrong way round. The piece is scrap, because the long point ended up on the wrong end.
Make it a habit: with every measurement, write down what happens at each end as well as the length. Something like “window wall, 92, inside corner left, outside corner right”. Then lay the piece down in the room the way it will hang, look at where the room is, and only then cut. Still unsure? Hold it against the wall: at an outside corner the face you can see has to be the longer one.
Do not want to miter? There are corner blocks
Mitering is not the only route. Pre-made inside and outside corner pieces are sold for most baseboard profiles, and they let you get away with square cuts only, which any saw can manage. The same goes for plinth blocks at door casings.
Two things to watch. Corner pieces are made per profile and per height, so you have to pick them to match the baseboard you are actually buying, not afterwards. And they take up length themselves, so your baseboard pieces come out shorter than the wall. Measure that on the piece you buy and allow for it before you cut.
Measure every wall separately
It is tempting to measure the room once and work the rest out on paper. Do not. Rooms are rarely square and opposite walls are rarely the same length. A sixteenth of an inch is invisible in the room but very visible in the corner where the baseboard does not close up.
So measure wall by wall, write it down with the name of the wall next to it (“window wall”, “closet wall”), and keep those names all the way to the saw. Then you know where every cut piece belongs.
The floor is not flat, and the baseboard goes on the wall
In almost any house the floor runs a little high or low somewhere. Baseboard cut dead straight will then leave a gap you only notice once it is against the wall. Three ways round it: scribe the bottom edge and follow the floor, caulk the top edge, or run shoe molding or quarter round along the bottom.
More important, and this is the expensive one: fasten the baseboard to the wall, never to the floor. A floating laminate or click vinyl floor has to be able to move, which is why it is laid with a 1/4 to 3/8 inch expansion gap along the wall, and the baseboard is what covers that gap. Nail into the planks and you pin the floor in place, and it will buckle or open up seams. For the same reason, do not caulk the bottom edge of the baseboard to a floating floor either. If you add shoe molding, nail it into the baseboard, not into the floor.
Bring MDF baseboard inside a couple of days before you fit it and let it sit in the room. MDF and wood move with humidity, and whatever still wants to shrink will pull your joints open after it is up.
Where the baseboard stops: the door casing
Every room has a door, and that is where the baseboard ends. That is not a miter but a square cut, tight against the casing. So measure that wall to the casing, not to the wall behind it.
It gets awkward when the baseboard is thicker than the casing, because then it stands proud and looks unfinished. You solve that with a plinth block beside the casing for the baseboard to die into, or you plane the last bit of baseboard down so it runs out neatly. Check that before you cut, because afterwards there is not much you can do.
From measurements to stock lengths: how much do you need?
Now that you have the measurements, the second question: how many lengths do you buy? The temptation is to add up all the wall lengths and divide by the length you buy. That almost always comes out short.
Here is why. With sheet goods you lay parts out in two directions and something usually still fits in a leftover corner. With baseboard there is only one direction. A length that is two thirds used simply leaves an end that is too short for the next wall. That is exactly where the saving is: by combining the pieces you often save a whole length. Two 47 inch walls fit on one 8 foot length, but only if you put them together. Twice exactly 48 inches does not: add the kerf and you go just past the 96 inches.
The kerf counts for more here
Every cut takes a little material away. On a miter saw or in a miter box that is less than a circular saw takes out of a sheet: reckon on about 1/8 inch, and measure your own blade if you want to be sure. On an 8 foot length that you get seven pieces out of, that is already close to an inch, which is just enough to leave your last piece short. So count that kerf in per cut, not as one fixed allowance at the end.
When is an offcut still worth keeping?
That is your call, and it is a real one. Set the limit low and you end up with a pile of short ends you throw out anyway. Set it high and the tool counts more as waste, and you may buy a length too many. For baseboard somewhere around 6 to 12 inches is a fair limit: shorter than that rarely fits beside a door or under a window.
Do not cut short pieces freehand. Miter saw manuals draw the line at around 8 inches: below that you cannot hold the piece safely and you cannot clamp it properly. Clamp a piece that short, or cut it off a longer length against a stop block, and keep your hand at least 6 inches from the blade.
What is left over and still usable does not have to go in the bin. See reusing offcuts.
Stock lengths, splices, and why you buy one extra
If one wall is longer than the longest length your store sells, you are stuck: that piece fits nowhere. A splice in the middle of a wall shows. In that case it pays to look for a longer size, and here US stores are kinder than European ones: 8 foot is the standard, but 12 and 16 foot are commonly stocked in the same profiles, and lumberyards will often go longer still. Check before you cut, because a 14 foot wall out of 8 foot stock always means a joint.
If you do have to splice, do not put the joint in the middle of the wall but near a corner, and cut it at an angle rather than square. This is called a scarf joint: two 45 degree cuts overlapping each other. A scarf joint is far less visible than a butt joint, it does not open up into a gap when the wood shrinks, and you can nail through the overlap.
And however neatly you have figured it: buy one length extra. A miter will go the wrong way, or a corner will turn out further off square than you thought. That one length is cheaper than a second trip to the store, and if you do not use it you return it or it goes on your offcut shelf.
The same works the other way round: sometimes a short length for the small pieces is cheaper than breaking into another long one. Price both before you buy.
How you do it in cutlistlab
In the Linear tab you work with lengths instead of sheets. It takes four steps:
- Pieces. One line per wall: a name, the length and the quantity.
- Stock lengths. The length you buy in, and what it costs. More than one length is fine.
- Settings. The kerf of your blade and the limit above which an offcut is still usable.
- Cutting order. Numbered per length, with the measurement beside it, to tick off at the saw.
You see straight away how many lengths you need, what it costs and what is left over. If a piece does not fit on any length, the app says so instead of quietly dropping it. Under Export there is What do I need: the shopping list to take to the store.
Frequently asked questions
Do I measure baseboard along the wall or along the front?
Look at it from above: the dimension you see from up there is the one that counts. For baseboard standing against the wall that is its thickness, usually 1/2 to 5/8 inch. For a batten lying flat it is the width instead. At an inside miter the back is the long point, so you simply measure the wall. At an outside corner the front is the long point, so that dimension gets added once per outside corner. Cope the joint instead and it comes off.
What angle do you set the miter saw to for baseboard?
Half of how far the baseboard changes direction at the corner, which is (180 minus the corner angle) divided by two. A miter saw and a miter box both count up from a square cut, not from the wall. A 92 degree corner is 44 on the saw, an 88 degree corner is 46. Only at a true 90 degree corner do both ways of figuring it land on 45. A miter box only gives you 45, because its slots are fixed.
Do you nail baseboard to the wall or to the floor?
To the wall. A floating laminate or click vinyl floor has to move, which is why it is laid with a 1/4 to 3/8 inch expansion gap that the baseboard covers. Nail into the planks and you pin the floor in place, and it will buckle. Do not caulk the bottom edge to a floating floor either, for the same reason.
How much baseboard do I need?
Measure every wall separately and add the lengths up. Do not just divide that by the length you buy: an 18 inch offcut is usually too short for the next wall, so in practice you need more pieces than the division suggests. Lay the pieces out over the stock lengths first, then add one extra length for the cut that goes the wrong way.
Can cutlistlab lay out boards, battens and trim as well as sheets?
Yes. The Linear tab works in lengths instead of sheets, so anything sold by the running foot: baseboard, battens, framing, bars and trim. You cut the corners yourself; the app works out the lengths.
Does the saw kerf matter when cutting to length?
Yes, and more than you would think. Every cut takes a little material. Take seven pieces out of one 8 foot length and you have lost most of an inch, which is enough to leave your last piece short. cutlistlab counts the kerf per cut so that does not happen.