Carpet Calculator

Last updated: June 2026

Room length

Room width

Carpet roll width

Add fitting allowance?

Room area

12 m²

Carpet to order

16.4 m²

Roll cut

1 strip(s), 4.1 linear m

Formula

Adjusted dimensions add fitting allowance. Strips = ceiling(adjusted width / roll width). Carpet area = strips x adjusted length x roll width.

About this calculator

Estimate how much carpet to order from a 4m, 5m, or custom-width roll. Unlike boxed flooring, carpet is cut from a roll, so the required order depends on strip width as well as room area.

Carpet roll method

The calculator uses metric dimensions and practical UK planning assumptions. Results are estimates, so check product labels, site conditions, and supplier guidance before ordering materials.

adjusted length = room length + fitting allowance
strips = ceiling(adjusted width / roll width)
carpet area = strips x adjusted length x roll width

How to use the carpet calculator

Choose the project type or measurement mode where the calculator offers one.
Enter all dimensions in metric units.
Add allowances such as coats, waste, pattern repeat, roll width, or bag size where relevant.
Review the main highlighted result first.
Check secondary results such as packs, bags, rolls, posts, or tin combinations.
Round up to supplier pack sizes and confirm the label coverage before buying.

Worked examples

Room fits one 4m roll width

Input: 4m x 3m room, 4m roll, fitting allowance on

Calculation: Adjusted width 3.1m fits one strip. Area = 1 x 4.1 x 4.

Result: Order about 16.4m² from a 4m wide roll.

Room needs two strips

Input: 5m x 4.2m room, 4m roll

Calculation: Adjusted width exceeds 4m, so 2 strips are needed.

Result: Order is based on two roll-width strips, creating more waste.

How carpet is measured and sold

Carpet is commonly sold from 4m or 5m wide rolls in the UK. The fitter cuts a length from the roll, so a room can require more carpet than the floor area suggests.

Underlay calculator note

Underlay is normally estimated by floor area rather than roll-width carpet cuts. Use the room area as a starting point and check the underlay roll or pack coverage.

Common mistakes

Mixing centimetres, millimetres, and metres without converting first.
Ordering exact quantities with no allowance for cuts, waste, damage, or uneven surfaces.
Forgetting that products are sold in tins, packs, bags, rolls, or boards rather than exact calculated quantities.
Using average deductions or coverage rates when the project has unusual shapes, textures, slopes, or access limits.
Not checking manufacturer instructions before final ordering.

Home improvement estimate disclaimer

This calculator is for general DIY planning only. It is not a substitute for a professional survey, structural design, building control advice, manufacturer instructions, or installer measurement.

Actual product coverage and pack sizes vary by supplier.
Site conditions can change material quantities.
Structural, roofing, electrical, gas, and regulated building work may need qualified advice.

Frequently asked questions

Why is carpet to order higher than room area?

Because carpet is cut from fixed-width rolls. If the room width does not fit neatly, offcuts and joins can increase the order area.

Should I use 4m or 5m carpet?

The better width depends on room dimensions, joins, pattern direction, and fitting preference. Compare both where possible.

Does this include stairs?

No. Stairs need a separate measuring method because tread, riser, landing, and pattern direction matter.

What is fitting allowance?

It is a small extra allowance around the room so the fitter can trim cleanly at edges.

Can this replace a fitter measurement?

No. Use it for planning and budgeting. A fitter should confirm final measurements before ordering.

Related calculators

Flooring Calculator
Paint Calculator
Area Calculator

What does this mean?

This calculator is designed to help you understand the likely number before you make a decision or start an application.

Your result should be checked against official UK guidance, especially if your circumstances include dependants, exemptions, prior leave, or a complex immigration history.

Treat the figure as a planning tool rather than legal advice. Where the answer affects an application deadline or major payment, speak to an authorised adviser.