Carpet Roll & Seam Calculator — Cutting Plan for Fitters

See how the room comes off the roll, where the joins go and what you waste, before you order.

Quick answer

Divide the room width by the roll width and round up to get the number of drops; each drop is the room length plus trim. Linear metres = drops × cut length, and carpet to order = linear metres × roll width. Try both ways round and pick the one with the least carpet and fewest joins.

Definition

A carpet roll calculator (or carpet cutting plan calculator) works out how a room is cut from a broadloom roll: how many widths (drops) you need, how long each cut is, where the joins fall and how much carpet is left over.

Explanation

Carpet comes in fixed roll widths, usually 4 m and 5 m in the UK. If the room is narrower than the roll, it comes off in one piece. If it is wider, you need a second drop and a join. Because the roll width is fixed, the same room can need very different amounts of carpet depending on which way the drops run and which roll width you choose. Add a trim allowance to every cut so you can fit to the walls.

Advantages

Shows the cheaper way round before you order
Counts the joins so you can keep them out of doorways
Flags offcuts big enough for a cupboard or a step

Disadvantages

Works on rectangles; split L-shaped rooms into rectangles or use a floor planner
Pattern repeats need extra on top of the plain trim allowance

Same 5.2 m × 4.3 m room, different rolls

Roll	Drops	Carpet to order	Joins
4 m roll (best way round)	2 × 4.40 m	35.2 m²	1
5 m roll	1 × 5.30 m	26.5 m²	None

Worked example

A 5.2 m × 4.3 m lounge on a 4 m roll needs two drops of 4.40 m (35.2 m², one join). On a 5 m roll it fits in one drop of 5.30 m (26.5 m², no join), which saves 8.7 m² of carpet.

Examples

Bedroom 3.4 m × 3.1 m on a 4 m roll: one drop of 3.20 m with the drops running along the 3.1 m side (12.8 m²), no join, leaving a 0.6 m offcut strip.
Through lounge 7.2 m × 3.6 m on a 4 m roll: one drop of 7.30 m along the length (29.2 m²), no join.

Summary

Check both ways round and both roll widths before you quote. In PlanCutFit the floor planner does this for every room on the job, including L-shapes and stairs, and draws the cut plan for you.

Frequently asked questions

How much trim should I allow per cut?

Most fitters allow 5–10 cm on each end of a cut (10 cm in total is a common default) for trimming into the walls. Allow more for out-of-square rooms.

Which way should the pile run?

Usually towards the main light or along the room’s length, and the same way in every room that meets, so the shading matches. Fixing the pile direction can cost more carpet; the calculator shows you how much.

Where should carpet joins go?

Away from doorways and main walkways, and ideally running towards the main window so they are less visible.