The method

How this calculator works

Find the length of wall to cover

For a rectangular room, the walls add up to 2 × (length + width). Measure each wall along the floor, because an out-of-square room can differ from the figures you expect. If the room has alcoves, a chimney breast or a bay, add the extra length of those walls.

Skirting stops at a door frame, so take off the width of each door opening. Leave in the length behind radiators and units unless you will not fit skirting there.

Allow for joints and corners

Internal corners are usually scribed (cut to follow the profile of the board next to them) and external corners are mitred. Both use up extra length, and cutting mistakes happen. A 10% allowance is a sensible default for a simple room.

The calculator treats boards as one continuous run and rounds up to whole boards, assuming you can reuse offcuts on other walls. If your longest wall is longer than a board, plan where the joints will fall, ideally away from the most visible spot.

Check the profile and the finish

Board lengths and profiles vary, so use the length given for your product. If the skirting will be painted, buying primed boards saves a coat, and paint quantity for woodwork is small enough that a single tin is usually plenty.

Fit the skirting after the floor. Leave the gap the flooring manufacturer asks for, and make sure the board covers the expansion gap along its full length.

Worked example

Example: a 4 m × 3 m room with one 80 cm door

  1. The walls add up to 2 × (4 + 3) = 14 m.
  2. Take off the door opening: 14 − 0.8 = 13.2 m.
  3. Add 10% for joints and waste: 13.2 × 1.1 = 14.52 m.
  4. With 2.4 m boards, 14.52 ÷ 2.4 = 6.05, which rounds up to 7 boards.

Practical answer: Buy 7 boards of 2.4 m. Six boards would only just fall short of the length with allowance, so the seventh also covers any mistakes.

Before you buy

Common measuring mistakes

  • Using the floor area instead of the length of the walls.
  • Forgetting to take off door openings, or counting the architrave as skirting.
  • Leaving out chimney breasts, alcoves and bays, which can add several metres.
  • Buying exact lengths with nothing spare for mitres, scribing or a split board.
  • Using a board length that does not match the product you intend to buy.