Skirting board & coving calculator
Measure the room, take off doorways (skirting and dado rails stop at them; coving and picture rails run above), add chimney breasts and alcoves, and get the number of lengths to buy with a waste allowance, the joins on long walls and the cost.
The room
Boards
About the skirting board & coving calculator
Measure the room, take off doorways (skirting and dado rails stop at them; coving and picture rails run above), add chimney breasts and alcoves, and get the number of lengths to buy with a waste allowance, the joins on long walls and the cost.
Part of SmartCalcy’s home & construction tools. It runs in your browser with no account, uses your own currency and units (change them at the top of the page), and gives estimates for information only, so check official guidance before you rely on a result.
How to use the skirting board & coving calculator
What it calculates and when to use it
Works out how many lengths of skirting board (baseboard), dado rail, picture rail or coving (crown moulding) to buy for a room, with doorways, extra runs, waste, joins and cost.
How to use it, step by step
- Choose the type of trim.
- Enter the room length and width, and any extra runs such as chimney breast sides.
- For skirting and dado, enter the doorways and their width.
- Enter the board length, waste and price, and read the lengths to buy.
What each input means
- Type of trim – Skirting and dado stop at doorways; picture rail and coving run above them.
- Room length and width – Starts at 4.5 × 3.5 m.
- Extra runs – Chimney breasts, alcoves, bays.
- Doorways – Starts at 1, 0.9 m wide including the architrave.
- Board length – Starts at 4.2 m.
- Waste – Starts at 10%.
How to read the results
- Lengths to buy – Whole boards, with the run to fit and the cost.
- Joins on long walls – Walls longer than one board need a joint.
- Internal corners – Four in a rectangular room.
The formula
Run = 2 × (length + width) + extra runs − doorways (skirting and dado only). Lengths = run × (1 + waste) ÷ board length, rounded up.
A worked example
With the starting entries: perimeter 16 m, minus a 0.9 m doorway = 15.1 m; with 10% waste 16.61 m; 16.61 ÷ 4.2 = 3.95, so buy 4 lengths. Each 4.5 m wall needs one join.
Assumptions and limits
- The room is a rectangle; add other walls as extra runs.
- Offcuts are only reusable when long enough, so short walls can waste more.
Common mistakes
- Deducting doorways for coving, which runs above them.
- Forgetting chimney breast returns.
- Buying exactly the run with no allowance for mitres.
Frequently asked questions
Do I deduct doors for coving?
No. Coving and picture rail run above the doors.
How do I join two boards on a long wall?
With a scarf joint: both ends cut at 45° and overlapped.
What length should I buy?
The longest you can transport, so there are fewer joins.
Related tools
How it adds up
- Perimeter
- 16 m
- Doorways
- −0.9 m
- Trim to fit
- 15.1 m
- With waste
- 16.61 m
- Joins on long walls
- 2
- Internal corners
- 4