Skirting Board & Architrave Calculator

How Many Lengths of Skirting Board Do I Need?

The quick answer is the total run of skirting divided by the board length, plus some spare. It gets that answer wrong in three places. Boards cannot bend round a corner, doors take a gap out of a wall, and an offcut is only worth keeping if it is long enough for another piece.

So this calculator plans the job the way you would cut it. It works out the runs of skirting on each wall, splits any run longer than a board into pieces, and then packs all the pieces into boards, longest first, so short pieces come out of the offcuts of long ones. A 4m × 3m room with no doors on 3m boards needs 5 boards in the cutting plan, which is 6 once 5% spare is added.

Stock lengths vary by merchant, so check before ordering. Wickes lists primed MDF skirting in 2.4m and 3.66m lengths, and Jewson lists 4.2m. Softwood is often sold in variable lengths, so use a custom length if your supplier quotes a range.

How to Measure a Room for Skirting

1. Measure each wall in full, corner to corner, at floor level. Do not subtract doors yourself, the calculator does that from the door details.
2. Go round the room one way and enter the walls in that order. For each wall, say whether the corner at its far end is internal or external. A plain box room is four internal corners.
3. Count a chimney breast as three walls. Its two sides and its front all get skirting. The corners where it meets the main wall are internal, and the two front corners are external.
4. Add each door. Choose the door size, the wall number, and the distance from the start of that wall to the near edge of the door.
5. Pick a board length and compare it with the ranking table under the results.

A closed room with square corners always has 4 more internal corners than external ones. If your numbers do not add up that way, the calculator tells you, because it usually means a wall or a corner type is wrong. Panelling the wall above the skirting? Our wall panelling calculator spaces the frames evenly and works out the strips. Fitting a laminate floor first? Our laminate flooring calculator leaves the expansion gap that the skirting covers, and counts the packs. Slat panels on the wall above? Our slat wall panel calculator counts the panels. New kitchen worktops? Our kitchen worktop calculator plans the boards round the corners. Adding a dado or picture rail? Our dado and picture rail calculator works out which doors and windows break it at its height.

The Rules the Calculator Uses for Joins and Corners

We state these here so you can check them against how you would cut it yourself.

• Shortest piece: 300mm, when a run is split. If the last piece of a split run would be shorter than this, the piece before it is shortened so both are usable. A run that is short on its own is left alone. In the default room the stretch between a corner and a door architrave is only 125mm, and it stays as it is. You can change the figure.
• No join within 300mm of a door. This applies when a run that ends at a door has to be split. Joins next to architrave are the ones that show. You can change the distance.
• External corners add 20mm to each run end that meets one, because the long point of an external mitre overshoots the corner line by about one board thickness. Internal corners are scribed or butted, so they add nothing.
• Saw cuts cost 3mm between two pieces cut from the same board.
• Skirting stops at the architrave. The gap at a door is the door width plus the reveal and architrave width on both sides. Untick the architrave option and skirting stops at the door frame instead.

What it does not do: it does not track which end angle an offcut has. A mitred offcut can only serve a piece that needs the same angle, so a real cutting plan can need slightly more than this one. That is what the waste allowance is for. See how we calculate for more on where our calculators simplify.

How Architrave Is Worked Out

A door needs two legs and a head. The top ends are mitred, so each length is measured to its long point.

• Leg = door height + reveal + architrave width
• Head = door width + 2 × reveal + 2 × architrave width

The reveal is the small setback of the architrave from the inside edge of the door lining. We default to 6mm and a 69mm architrave, and both are editable, so set them to match your own job. With the defaults, a 1981 × 762mm door has legs of 2056mm and a head of 912mm. The calculator shows this working next to the result for every door size in the room.

Legs and heads are then packed into boards the same way as skirting. The count you see is the cutting plan count with no percentage on top, because that is the honest number. A spare board is shown on its own line for you to add or not. On 2.4m boards a leg leaves an offcut of only 344mm, too short for a head or another leg, which is why a single set can need more boards than you would guess from the total length. Trim both sides of the door and the count roughly doubles.

Architrave comes in shorter lengths than skirting. Wickes lists 2.1m architrave (sold singly) and 2.2m (in packs of five), and a 2056mm leg fits in either, so the calculator offers both and ranks every length for your doors. A 2.1m board leaves only 44mm on that leg, so there is no room for a miscut. The calculator flags any length that leaves under 100mm spare on a leg or head. B&Q lists National Skirting architrave in 3040mm and 4200mm lengths, so 3.04m and 4.2m are in the list too. Some online specialists, such as Skirting World and Skirting UK, sell door sets instead: two 2440mm legs and a 1220mm head, covering one side of a single door. A set is three uncut lengths, not pre-mitred pieces, and a wider opening needs their double-door set. If you buy sets, you need one per side of each door.

Which Board Length Wastes Least?

The calculator runs your room against 2.4m, 3.0m, 3.66m, 4.2m and your custom length if you set one. It ranks the results by the metres you would buy after the waste allowance, then by the fewest joins. The top of the list is the length that wastes least for your walls.

Architrave gets its own ranking, because its stock lengths (2.1m and 2.2m as well as 2.4m) differ from skirting. Two things the rankings cannot tell you. Price per metre differs by length and merchant, so a shorter board with a lower price can beat a longer one on cost even when it wastes more. And a 4.2m board is a long thing to carry through a house and up a stairwell, so the least wasteful board on paper is not always the easiest to use.

Standard UK Internal Door Sizes

The dropdown uses these sizes. Figures are from Door Superstore's UK size chart. 1981 × 762mm is the most common internal door in England and Wales. Scottish doors are taller.

Double doors and non-standard openings: pick Custom and type the total width.

Common Room Sizes: Skirting and Architrave Needed

Generated from the calculator above. Each room is rectangular with four internal corners, one 762mm door on the second wall, 5% skirting waste, 69mm architrave with a 6mm reveal on one side of the door. Architrave is 2.4m boards, counted from the cutting plan with no spare.

Use the calculator for your own room. A chimney breast, a bay or a second door changes the answer more than you would expect.

Frequently Asked Questions

How many lengths of skirting board do I need?

Add up the runs that actually get skirting, wall by wall, not just the room perimeter. Each door takes a gap out of its wall, a run longer than one board needs joins, and a short piece can often come out of the offcut of a longer one. This calculator plans it that way and then adds your waste allowance. For a 4m × 3m room with no doors and 3m boards it comes to 6 boards (5 planned plus 5% spare), even though the perimeter alone is 14m.

How much skirting do I take off for a door?

Skirting stops at the architrave, not at the door itself. So the gap is the door width plus the architrave on both sides. With a 762mm door, 69mm architrave and a 6mm reveal, that gap is 912mm. The calculator works this out from your own door size and architrave width instead of taking a flat 800mm off every door.

How much architrave do I need for one door?

One set is two legs and a head. The legs are the door height plus the reveal plus the architrave width, because the top end is mitred. The head is the door width plus two reveals plus two architrave widths. For a 1981 × 762mm door with the defaults above, each leg is 2056mm and the head is 912mm. With 2.4m boards that is 3 boards for one set, and 5 boards if you trim both sides of the door. That is the cutting plan count with no percentage added, and the calculator shows a spare board on its own line if you want one. Change the reveal and architrave width to match your job and the working shows next to the result.

What length of skirting board wastes least?

It depends on the room, so the calculator runs your walls against each stock length and ranks them by metres bought, then by fewest joins. A longer board is not always better. If your walls are mostly 3m, a 3m board leaves almost nothing, while a 4.2m board leaves a big offcut on every wall. Stock lengths vary by merchant, so check before ordering. Also think about carrying: a 4.2m board is awkward to get through a house and up a stairwell.

Where should the joins in skirting board go?

Away from doors and not right next to a corner. When it splits a run into pieces, this calculator will not put a join closer than 300mm to a door, and will not leave a piece shorter than 300mm. A run that is short on its own, like the gap between a corner and a door, stays as it is. Both distances are editable. Joins are best made as a scarf joint, an overlapping 45 degree cut, so the join stays closed if the boards move a little.

Should I mitre or scribe skirting board corners?

External corners are always mitred. Internal corners can be mitred or scribed, where one board runs square into the corner and the second is cut to the profile of the first. Scribing tends to stay tighter in older houses where walls are not square. The calculator adds 20mm to each run end that meets an external corner, since the long point of the mitre overshoots the corner line. Internal corners get no allowance.

Why does the calculator say more boards than perimeter divided by board length?

Because boards cannot bend round a corner and offcuts are only useful if they are long enough for another piece. A 4m wall on 3m boards needs a full board plus a 1m piece, and that piece then has to come from somewhere. The calculator packs every piece into boards, longest first, and only starts a new board when nothing else has room.