Skirting board calculator
How many whole lengths of skirting board to buy for a room, worked out from a cutting plan for each wall.
How the number is worked out
- Measure each wall. Along the floor, corner to corner, including across the doorways.
- Add 5 cm to each wall for the corner cuts.
- Join the long walls. A wall longer than a length takes whole lengths, then a short end joined on. Each join takes another 5 cm.
- Cut the short pieces from as few lengths as possible. The longest first, each from the first length it still fits in.
- Count the lengths. The whole ones, plus the ones the short pieces are cut from.
A worked example
A room 4.2 m by 3.6 m with one doorway 0.8 m wide, and skirting sold in 2.4 m or 3 m lengths. These are example figures, not a product. The doorway is not taken off.
| Working | 2.4 m lengths | 3 m lengths |
|---|---|---|
| Distance round the room | 15.6 m | 15.6 m |
| Distance divided by the length, rounded up | 7 | 6 |
| Whole lengths along the walls | 4 | 4 |
| Short ends to cut, in metres, with their allowance | 1.9, 1.9, 1.3, 1.3 | 1.3, 1.3, 0.7, 0.7 |
| Lengths the ends come from | 4 | 2 |
| Lengths to buy | 8 | 6 |
| About left over | 3.2 m | 2 m |
Dividing the distance round by the length says 7 lengths of 2.4 m. The cutting plan needs 8, because no two of the short ends fit in one length. The length sold changes the count: the same room takes 6 lengths of 3 m. Enter the length on your shelf's label.
Mistakes that cost a length
- Dividing the distance round by the length. In the example it says 7 lengths of 2.4 m, and the walls need 8.
- Leaving out the allowance for corners and joins. Each wall needs 5 cm more than its own length, and each join another 5 cm.
- Choosing the length without working it out. The example takes 8 lengths of 2.4 m or 6 of 3 m.
- Joining an architrave leg. A leg is never joined. If the door's height plus 5 cm is more than the length sold, choose a longer length.
- Buying lengths from different batches. The profile and the finish can differ between batches and makers.
Questions
Is the doorway taken off?
No. A door splits a wall into two short runs, and they usually come out of the same lengths as the whole wall would. Counting the whole wall errs towards a spare length rather than a wall left short.
Why does the plan need more lengths than the distance divided by the length?
Every wall needs its own pieces, and the offcuts left after cutting the ends are often too short for any other wall's end. The plan shows what each length is cut into.
Does it count architrave?
Yes, from the doors you enter: two legs and a head on one side of each door. The other side belongs to the next room. A leg is never joined.
Which lengths does it start with?
2.4 m for skirting and 2.1 m for architrave. They are labelled examples, not a product. Change them to the lengths on your shelf's label.
Does it count adhesive, primer and paint?
It lists fixings, primer and a top coat, and caulk and filler, each marked Check first, because how much you need depends on the product. Its label says how far it goes.