What this calculator does
A carpet quote calculator works out the full cost of carpeting a room, not just the carpet itself. Carpet is normally sold and quoted by the square metre, so the starting point is the room area, but the number that actually lands on an invoice usually also includes underlay and the cost of having it laid.
The wastage allowance is the part people leave out when they estimate this themselves. Carpet comes off the roll in fixed widths, and a room rarely lines up perfectly with that width, so offcuts, pattern matching and awkward corners mean the carpet actually bought is somewhat more than the bare floor area. Leaving that out is the most common reason a DIY estimate comes in under the real invoice.
The formula
Multiply room length by width to get the floor area, then add the wastage allowance to get the carpet area actually needed. Multiply that area by the carpet price per square metre, and separately by the underlay and installation prices per square metre if those are being quoted, then add the three together for the total.
| Term | Meaning |
|---|---|
| Floor area | Room length × width, before any wastage allowance. |
| Wastage allowance | Extra carpet needed for offcuts and pattern matching, as a percentage of the floor area. |
| Carpet area | Floor area with the wastage allowance added: what is actually ordered and paid for. |
The inputs explained
| Field | What to enter |
|---|---|
| Room length (m) | The length of the room being carpeted. |
| Room width (m) | The width of the room being carpeted. |
| Wastage allowance (%) | A typical allowance is 5 to 15%, higher for irregular room shapes or patterned carpet. |
| Carpet price per m² ($) | The supplier price per square metre for the carpet itself. |
| Underlay price per m² (0 if not needed) ($) | The price per square metre for underlay, or 0 if it is not being quoted separately. |
| Installation price per m² (0 if not needed) ($) | The price per square metre for laying the carpet, or 0 if installation is not included. |
When to use it
Comparing two supplier quotes
Suppliers sometimes bundle carpet, underlay and installation differently. Entering each supplier’s per-square-metre prices separately here puts both quotes on the same footing before deciding between them.
Budgeting before choosing a carpet
Working out the total at a few different carpet prices per square metre shows how much a nicer carpet actually adds to the final bill once underlay and installation are already fixed costs.
Checking a tradesperson’s invoice
If a quote lists room dimensions and per-square-metre rates, recalculating the total independently is a quick check that the arithmetic and the wastage allowance applied match what was agreed.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the total changes with carpet price per m²
A 5 m by 4 m room, with underlay and installation held fixed, across a range of carpet prices.
| Carpet price per m² | Total quote | Carpet needed (with wastage) | Carpet cost |
|---|---|---|---|
| $25.00 | $990.00 | 22.00 m² | $550.00 |
| $35.00 | $1,210.00 | 22.00 m² | $770.00 |
| $45.00 | $1,430.00 | 22.00 m² | $990.00 |
| $55.00 | $1,650.00 | 22.00 m² | $1,210.00 |
| $70.00 | $1,980.00 | 22.00 m² | $1,540.00 |
| $90.00 | $2,420.00 | 22.00 m² | $1,980.00 |
How the total changes with the wastage allowance
The same 20 m² room and prices, across a range of wastage allowances.
| Wastage allowance | Total quote | Carpet needed (with wastage) |
|---|---|---|
| 0% | $1,300.00 | 20.00 m² |
| 5% | $1,365.00 | 21.00 m² |
| 10% | $1,430.00 | 22.00 m² |
| 15% | $1,495.00 | 23.00 m² |
| 20% | $1,560.00 | 24.00 m² |
| 25% | $1,625.00 | 25.00 m² |
Questions
Is carpet always priced per square metre?
It is the most common way carpet is quoted, but some suppliers price by the linear metre of a fixed roll width instead. If a quote uses linear metres, convert it to a price per square metre using that roll width before comparing it here.
What wastage allowance should I use?
A simple rectangular room with carpet running in one direction often needs as little as 5%. Irregular shapes, multiple rooms joined together, stairs, or a patterned carpet that needs matching across seams typically need 15% or more.
Do I need to include underlay separately?
Only if your supplier quotes it as its own line item. Some carpet prices are quoted already including underlay, in which case leave that field at 0 to avoid double counting it.
Why is the carpet area larger than the room area?
The wastage allowance accounts for the carpet that is cut away and cannot be used elsewhere: offcuts from fitting the roll to the room shape, allowance for pattern repeats, and trims around doorways and fixtures.
For a room being finished with tiles or floorboards instead of carpet, see the flooring calculator. To work out the area of an irregular room before pricing it here, the concrete volume calculator shows the same length-by-width area method applied to a slab.