Doors, Archs & Skirting Calculator

1. List the doors. One row for each door size: how many, the leaf width and height, single or a pair, archs on one side or both, a new lining or not, and 2 or 3 hinges a leaf.
2. List the rooms. The length and width, any extra walls such as chimney breast sides, bays or boxing, how many doorways and how many outside corners. An internal door is a doorway in both rooms it joins, and the calculator tells you if the two counts don't match.
3. Set your mouldings. The lengths your skirting and architrave come in, the architrave width, the reveal you leave on the lining and the gaps round the door.
4. Read off the list. You get the lengths to buy with your spares, the doors, lining sets, hinges, latches and handles, the skirting for each room with its corners and joints, and a cutting plan for every length. Copy the list or print it.
5. Price it if you like. Put in your own rates for hanging doors, fitting linings, archs and skirting, and your material prices, for a total before and after VAT.

How the lengths are worked out

An architrave leg runs from the floor to the outside of the mitre at the head: the gap under the door + the door height + the gap at the head + the reveal + the architrave width. For a 1981 mm door with 69 mm architrave, a 10 mm gap under the door, 3 mm at the head and a 5 mm reveal, that's 2,068 mm, so 2.1 m lengths work. A 2040 mm metric door needs 2.2 m lengths or longer.

The head is the width between the lining legs + twice the reveal + twice the architrave width, and the skirting stops at the outside edge of the archs either side. Every piece gets a little extra for trimming, and the pieces are fitted into your lengths longest first, so offcuts are used before a new length is cut.

A wall longer than one length is joined with a scarf joint. The doorways are taken out of the middle of the longest walls, so your real pieces can come out a little different. Always check the sizes on site before you cut.