Carpet Calculator UK — Area, Underlay & Gripper Rod

This UK carpet calculator considers the roll width to work out how much carpet you actually need to buy. Because carpet comes in a fixed width off the roll, the calculation is not simply floor area — you need to factor in the roll width and room orientation, then add a wastage allowance for trimming.

Measuring your room

Measure the room wall to wall at its longest and widest points, in metres. Measure into doorways up to where the carpet will finish (usually under the centre of the closed door) and treat alcoves, bay windows and chimney breasts as separate sections. Walls in older UK homes are seldom perfectly square, so take the largest reading. Enter the longest dimension as the length and the widest as the width.

L-shaped and irregular rooms

For an L-shaped room, press Add section and enter each rectangle as its own section: the calculator works out the roll cut for every section separately (each section is a separate piece off the roll, rounded up to the next 0.1m) and adds them together, so the total never under-orders. Use three sections for a T or U shape. Underlay rolls are also rounded up per section, and gripper rod uses each section's full perimeter, a deliberate slight over-count at the joins.

The formula

If room width ≤ roll width: Carpet length = Room length × (1 + Wastage %)

If room width > roll width but room length ≤ roll width: the carpet is turned 90° so the room length runs across the roll — no seam needed, and Carpet length = Room width × (1 + Wastage %)

If both room dimensions > roll width: multiple widths are needed and a seam is required

Carpet area (m²) = Carpet length × Roll width

Underlay and gripper

• Underlay: Standard UK roll 11m × 1.37m ≈ 15 m² per roll
• Gripper rod: Perimeter minus doorway openings (0.8m per standard door)

For rooms that are wider than the carpet roll, we calculate the number of widths needed and add the extra carpet accordingly. UK carpet is priced per m² (older suppliers may still quote per square yard — 1 square yard = 0.8361 m²), so knowing the actual area you need to purchase (which may be larger than the room area due to roll width constraints) is important for accurate budgeting. Enter your supplier's price per m² above for a cost estimate based on the carpet area, not just the floor area.