To measure for flooring, multiply the room’s length by its width, subtract any area you will not cover, add 5% to 15% for waste and divide by the coverage of one pack. To measure for fencing, divide the run by the width of a panel plus a post, round up, and add one more post than panels. The details below show how.
Measuring a room for flooring
Use a tape measure and write every number down with its unit.
- Measure the longest length and the widest width of the room, wall to wall, including door recesses and bay windows if you will floor them.
- If the room is not a simple rectangle, split it into rectangles, measure each and add them up.
- Measure any area you will not floor, such as an alcove, hearth or fitted unit, and subtract it.
- Multiply to get square metres. One square metre is about 10.76 square feet.
The How much paint, wallpaper or tile do you need? guide uses the same area sums for walls and tiles, and the Area and square footage calculator helps with unusual shapes.
Choosing a waste allowance
Cutting around walls, pipes and doorways wastes material, and the layout matters. The Flooring calculator calculator suggests these starting points, which you can change:
| Flooring | Straight lay | Diagonal | Herringbone or pattern |
|---|---|---|---|
| Carpet or vinyl | 5% | 10% | 15% |
| Laminate | 7% | 12% | 17% |
| Solid or engineered wood | 10% | 15% | 20% |
Rooms with many corners, stairs or patterned materials may need more. These are rules of thumb, not guarantees, and a fitter or the retailer can give a better figure for your room.
Worked example: a living room
We used the Flooring calculator tool for a room 5 m by 4 m with a 1 m by 0.8 m alcove left out, laminate with a 7% allowance, packs of 2.2 m² and a price of £20 per m².
- Room area 20 m², less 0.8 m², leaves 19.2 m² to cover.
- With 7% waste the need is 20.54 m².
- That is 10 packs, or 22 m² in total.
- At £20 per m² the cost is £440, with 2.8 m² left over for repairs.
Laying the same laminate diagonally with a 15% allowance needs 11 packs, which shows how much the layout can matter. Always check the pack coverage on the box, and buy all the packs from the same batch so the shades match. Underlay, trims and fitting are extra.
Measuring for fencing
Fencing is a counting job along a line. Walk the line with a tape or a measuring wheel and note where gates, corners and changes in level fall.
- Panel width: common panels are about 1.83 m (6 ft) wide, but check your supplier.
- Post thickness: each post takes up part of the run, so a bay is the panel width plus one post.
- Panels: (run − gates − one post) ÷ (panel + post), rounded up.
- Posts: one more than the number of panels for an open run, or the same number for a closed boundary. Each gate adds one post.
- Gravel boards: one per panel if you use them.
- Post-mix: posts multiplied by the bags each hole needs.
For a 12 m run with no gates, 1.83 m panels and 10 cm posts, the Fencing calculator calculator gives 7 panels, 8 posts, 7 gravel boards and 16 bags of post-mix at two bags per post. The last panel will be cut, because 7 bays are about 1.6 m longer than the run.
Corners, slopes and gates
Corners and gates are where counts go wrong. A corner post is shared by two sides, but each side will round to a whole number of panels, so measure each side separately for an accurate count. On a slope, panels either step down or are cut to follow the ground, which can need more panels than a flat measurement suggests. A gate needs two posts, and its width comes out of the run. Our How much concrete do you need for a slab or post holes? guide helps you estimate how much concrete each post hole needs.
Before you buy
- Check the panel height, the post length (the post must be long enough to go into the ground) and any rules on boundary height.
- Confirm who owns the boundary and whether you need permission or planning consent. Check with your local council.
- Buy a spare panel or one pack if you can, so you can repair damage later.
- Round every quantity up.
Note: these are general estimates. Measurements, pack sizes and local rules vary, so check them with your supplier and council before ordering.
Try the calculator
Enter your room sizes in the Flooring calculator calculator to get packs and cost, or your run length in the Fencing calculator calculator to count panels and posts.
Open the free Flooring calculator
Worked example 2: carpet versus herringbone wood
Two rooms show how much choice of material and layout matters. Both figures come from our flooring calculator tool.
A bedroom in carpet. The room is 3.6 m by 3 m, which is 10.8 m². With a 5% allowance you need 11.34 m². Carpet sold in 4 m² lengths means 3 packs, or 12 m² bought. At £18 per m² that costs £216, with 1.2 m² spare. (Carpet is often sold by roll width, so ask the supplier how they cut it.)
A dining room in wood. The room is 4.2 m by 3.4 m, which is 14.28 m². The table compares two layouts, with packs of 1.8 m² at £45 per m²:
| Layout | Waste | Area needed | Packs | Cost |
|---|---|---|---|---|
| Straight lay | 10% | 15.71 m² | 9 | £729 |
| Herringbone | 20% | 17.14 m² | 10 | £810 |
The pattern costs one more pack and £81 more in material, and fitting a pattern is usually slower as well, so ask for quotes with the layout specified.
Step-by-step: a good measuring routine
- Sketch the room and number each wall. A rough drawing makes it easier to catch mistakes.
- Measure each wall and note any differences, since few rooms are perfectly square.
- Use the larger measurements where two opposite walls differ.
- Mark obstructions, such as chimney breasts, units and pipes, and measure the area you will not floor.
- Convert units if the packs are in square feet. One square metre is about 10.76 square feet, so a 4 m² pack is about 43 square feet.
- Check the doorway. If flooring continues through a door, include the strip beneath it.
- Round up to whole packs, then confirm stock and batch numbers with the supplier.
Planning a fence: worked example 2
A 20 m run along a garden side with one 0.9 m gate, using 1.83 m panels and 10 cm posts, gives the following in our fencing calculator:
| Item | Quantity |
|---|---|
| Fence length excluding the gate | 19.1 m |
| Panels | 10 |
| Posts in total | 12 |
| Gravel boards | 10 |
| Post-mix bags (2 per post) | 24 |
| Spare length across the run | 0.3 m |
The 0.3 m of spare length is small enough to cut off one panel or to space the posts slightly wider. A closed boundary is different. A 30 m closed boundary with four corner posts needs 16 panels and 16 posts, because there are no end posts and every post joins two panels.
Common measuring mistakes
- Measuring only the widest part of an irregular room and forgetting to split it into rectangles.
- Forgetting the area under doors, in alcoves or inside a bay window.
- Ordering exactly the area needed with no allowance for cuts.
- Mixing packs from different batches, which can show as a different shade.
- Counting fence posts as equal to panels, and forgetting that an open run needs one more post than panels.
- Not allowing for a slope, which can change the panel count or need stepped panels.
- Missing out extras: underlay, trims, adhesive, concrete, post caps or gravel boards.
Buying and fitting extras
For indoor floors, factor in underlay, threshold strips, edge trims and a scotia or beading to cover expansion gaps. Some products need a gap around the walls so they can move with changes in temperature and humidity, so check the maker’s fitting instructions. For fences, consider the concrete for each post hole, which the How much concrete do you need for a slab or post holes? guide helps you estimate, and consider treatment or paint for the timber. If you are decorating at the same time, How much paint, wallpaper or tile do you need? covers walls and tiles.
When to check with a professional or official source
Ask a fitter to check a subfloor for damp or unevenness before laying. For fences, local rules can cover height, the front of a property, listed buildings and shared boundaries, so ask your council and read your property deeds. Check any utility lines before you dig post holes.
Frequently asked questions
How much extra flooring should I buy?
Many people buy 5% to 10% extra for a straight lay and 10% to 15% or more for diagonal or patterned layouts. Rooms with lots of corners need more.
Do I measure to the wall or the skirting board?
Measure to the walls for a safe estimate, since flooring often runs under skirting or is covered by trims. Include door recesses if you will floor them.
How many fence posts do I need for 10 metres?
It depends on the panel width. With 1.83 m panels you need six panels and seven posts for an open run, but use the calculator to include post thickness, gates and corners.
What if my fence run is not a whole number of panels?
You can cut the last panel, or space the posts slightly wider if the panels allow it. The calculator shows the spare length so you can choose.
How do I measure an L-shaped room?
Split it into two rectangles, measure each and add the areas. Do not multiply the overall length by the overall width, as that includes the missing corner.
How many square feet are in a square metre?
About 10.76. To go the other way, divide square feet by 10.76.
How wide should I make the gap for a gate?
It depends on the gate. Measure the gate itself, then ask the supplier what clearance the hinges and latch need. The calculator subtracts the opening you give it from the run.
Should I buy spare flooring?
Yes, if you can. Keeping a spare pack from the same batch lets you replace a damaged plank or tile later, since discontinued lines can be hard to match.