# Carpet and Vinyl Roll Calculator: Drops, Seams and Roll Length

> Broadloom carpet and sheet vinyl come off a roll of fixed width, so they are ordered by running length, not by area. The room is covered in drops: the number of drops is the distance across the room divided by the roll width, rounded up, and each drop is the length of the room plus trim and any pattern allowance.

## What it calculates

For a rectangular room covered in broadloom carpet or sheet vinyl from a roll, the
calculator gives:

- the number of **drops** (full-length pieces) across the room;
- the **drop length**, with trim and any pattern allowance;
- the **roll length to order**, in running metres;
- the **area ordered** against the room area, and the **offcut** as a share of it;
- the number of **seams**.

It also shows the same figures for the other lay direction, so the two can be compared.
For carpet tiles, vinyl planks or tiles, use the
[flooring quantity calculator](/calculators/flooring-quantity-calculator), which counts
pieces and boxes.

## Inputs

**Room length** and **width** are in metres; the equivalent in feet is shown under each.

**Product** chooses broadloom carpet or sheet vinyl. It only sets a starting roll width,
4 m for carpet and 2 m for vinyl, which you can change.

**Lay direction** sets whether the drops run along the room length or along its width.

The **assumptions** panel holds the roll width, the trim allowance at each end of a drop,
the pattern match allowance and the wastage on the roll length.

## Method

1. Across = the room dimension the drops are laid side by side across; run = the other one.
2. Drops = across ÷ roll width, rounded up.
3. Drop length = run + 2 × trim + pattern allowance.
4. Roll length = drops × drop length × (1 + wastage), rounded up to the next 0.1 m.
5. Area ordered = roll length × roll width.
6. Offcut = (area ordered − room area) ÷ area ordered.
7. Seams = drops − 1.

## Assumptions

| Assumption | Default | Notes |
| --- | --- | --- |
| Roll width, carpet | 4 m | Illustrative; replace with your product's data sheet |
| Roll width, sheet vinyl | 2 m | Illustrative; replace with your product's data sheet |
| Trim at each end of a drop | 0.1 m | For scribing to the wall |
| Pattern match allowance | 0 m | One pattern repeat per drop for a patterned product |
| Wastage on roll length | 3% | Squaring the roll end, handling damage, a small spare |

## Limitations

- **Rectangular rooms only.** Split an L-shaped room into rectangles, or plan the drops on
  a drawing.
- **Offcuts are not reused.** In practice a wide offcut can sometimes fill a corridor or a
  recess; the calculator counts every drop as cut fresh from the roll.
- **Bays, columns and doorway extensions are not included.** Add their area as extra drops
  or extend the run.
- **One roll is assumed.** Large rooms may need more than one roll, and drops from
  different batches should not sit side by side; order enough from one batch.
- **Underlay, adhesive, gripper, seam welding rod and subfloor preparation** follow the
  manufacturer's instructions and are not counted.

## Worked example

An 8 × 6 m room (26.2 × 19.7 ft) in broadloom carpet from a 4 m roll, drops along the 8 m
length, 0.1 m trim at each end, no pattern and 3% wastage:

| Step | Calculation | Result |
| --- | --- | --- |
| Room area | 8 × 6 | 48 m² (517 sq ft) |
| Drops | 6 ÷ 4, rounded up | 2 |
| Drop length | 8 + 2 × 0.1 + 0 | 8.2 m |
| Roll length | 2 × 8.2 × 1.03 = 16.892, rounded up | 16.9 m |
| Area ordered | 16.9 × 4 | 67.6 m² |
| Offcut | (67.6 − 48) ÷ 67.6 | 29% |
| Seams | 2 − 1 | 1, 8 m long |

The room needs **16.9 m of 4 m wide carpet in 2 drops, with one seam**. The second drop is
cut down to 2 m wide, which is where the 29% offcut comes from. Laying the drops along the
6 m width instead gives 2 drops of 6.2 m, **12.8 m of roll** (51.2 m²) and about 6%
offcut. The same room in 2 m sheet vinyl along the length needs 3 drops, 25.4 m of roll and
2 seams.

## How engineers use it

On a fit-out the floor finish is shown on a finishes layout, and the flooring contractor
prepares a seaming or cutting plan for each roll product. The plan places the drops so
seams avoid doorways, main routes and points where light rakes across the floor, keeps the
pile or pattern running one way, and nests offcuts into corridors and recesses. The order
comes from that plan, in whole running metres per batch.

## When a professional design must replace it

Use the calculator to check how much roll a room needs or to compare lay directions. Replace
it with a cutting plan from the flooring contractor before ordering, and wherever the room
is irregular, the product is patterned, several rooms share one roll, or seam positions
matter. Subfloor preparation and moisture testing follow the manufacturer's instructions
for the product chosen.

## Frequently asked questions

### How much broadloom carpet do I need for a room?

Divide the distance across the room by the roll width and round up to get the drops, then multiply by the drop length (room run plus trim at both ends). An 8 × 6 m room in a 4 m wide carpet, with drops along the 8 m length and 0.1 m trim at each end, needs 2 drops of 8.2 m, or 16.9 m of roll with 3% wastage.

### Why does the lay direction change how much I order?

The number of drops depends on the distance across the room, and the offcut from the last drop is wasted. In an 8 × 6 m room with a 4 m roll, drops along the length need 16.9 m of roll with 29% offcut; drops along the width need only 12.8 m with about 6% offcut. Seam position, traffic and light also decide the direction.

### What is a drop?

A drop is one full-length piece cut from the roll and laid across the room. Its length is the room dimension it runs along plus a trimming allowance at each wall and, for a patterned product, one pattern repeat so neighbouring drops can be matched.

### How many seams will the floor have?

One fewer than the number of drops. Two drops make one seam running the full length of the drops. The installer usually tries to keep seams out of doorways and main walking routes, and seams in sheet vinyl are welded or sealed to the manufacturer's instructions.

### Should I use this for carpet tiles or LVT planks?

No. Carpet tiles, vinyl planks and ceramic or vitrified tiles are counted by pieces and boxes, which the flooring quantity calculator does. This calculator is only for products cut from a roll: broadloom carpet and sheet vinyl.

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Source: https://hagerstone.com/calculators/carpet-vinyl-roll-calculator