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Building and garden · Areas

Estimate flooring area including offcuts

Net area is the room rectangle. A cutting margin is added (10% default, 25% at most) to match an order in boxes, planks, or tiles.

Calculate

Room length on the floor, in meters. Convert feet first if needed.

Room width. An L-plan: two rectangles, two calculations.

Cuts, breakage, layout. 10% default; more on a diagonal.

How the calculator works

L and W are in meters. Net area is L × W. The order multiplies by (1 + p/100). This margin is not a density or a paint spreading rate: it is layout offcuts, breakage, and leftover of a dye lot. Makers sell by the box (for example 1.68 m² or 20 sq ft): divide the increased area by one box and round up.

Formula and method

S = L × l

Net area in m².

Scommande = S × (1 + p / 100)

p is the offcut percent (0 to 25).

A rectangle is the base case. Niches, open closets, and partitions are handled by adding or subtracting rectangles. The percent depends on format and layout: a large rectified tile in a notched room, a diagonal set, or wide planks consume more than 10%. A simple room, planks parallel to the length, can drop toward 5–7%. Joints, baseboards, and thresholds are separate supplies.

Worked example

Bedroom 5 m × 4 m, 10% offcuts

L = 5 m, W = 4 m, p = 10%.

  1. Net area: 5 × 4 = 20.00 m² (about 215 ft²).
  2. Area to order: 20.00 × 1.10 = 22.00 m².
  3. If a box is 2.00 m²: 22 / 2 = 11 boxes. If a box is 1.68 m²: 22 / 1.68 ≈ 13.10 → 14 boxes.

22.00 m² to order for 20 m² on the floor.

Input notes

Length
Finished wall to finished wall, not the structural shell. Measure in several places: an out-of-square wall is taken at the longest.
Width
Second floor dimension. For a hall, length × width of the hall, without a neighboring room already counted.
Offcut allowance
10% for a standard straight set. 8–12% hardwood, 10–15% large-format tile, 15–20% diagonal. Maximum typed is 25%.

Assumptions and limits

Assumptions

  • Rectangular room, one level.
  • The margin covers cuts and breakage, not baseboards or adhesive.
  • The math stops at m²: rounding to boxes comes next.

Limits

  • Patterns (medallions, borders, herringbone) are not simulated.
  • A dye lot (hardwood, tile) may force buying more to stay even.
  • Screed or slab area is calculated separately (concrete tool): that is not the covering.

How to read the result

22 m² ordered for 20 m² on the floor is the 10% margin. Compare with m² (or sq ft) on the box and always round up: leftover of the same lot beats a top-up six weeks later, often a different shade. Sound offcuts serve closets and pipe cut-outs.

Common mistakes

  • Ordering net area with no offcuts.

    Edge cuts and breakage do not recycle into full planks. Add p, then round to boxes.

  • Keeping 10% for a diagonal set.

    A diagonal multiplies offcuts. Often go toward 15% or more depending on format.

  • Using wall area (paint) as floor area.

    The floor is L × W of the room. Walls are perimeter × height.

  • Forgetting to round to a whole number of boxes.

    22 m² / 1.68 m² per box is not an integer. Go to the next box.

Methodology · Sources

Related calculations

Frequently asked questions

Is 10% offcuts always enough?

For a rectangular room in a straight set, often yes. Not for a diagonal or large format in a cut-up plan.

Install notes and layout habits run around 5 to 15% depending on the product. 10% is a default. A bathroom with many cuts, a 120 cm tile, or very wide planks justify more. The calculator caps at 25%: beyond that, reread the plan rather than inflating the lump.

How do I treat an L-plan?

Two rectangles, two net areas, one margin at the end (or a margin per zone if layouts differ).

Add net areas before applying p, so the elbow is not counted twice. If one wing is diagonal and the other straight, split the margins. Thresholds between rooms may need a profile, not extra covering.

Is the tile joint in the area?

Floor area is the room’s. The joint slightly reduces tile area, but you still order on S_order.

A 2 mm joint on a 60 cm tile barely changes m². Pros order on room area plus offcuts, not on a theoretical mosaic of joints. Spacers and grout are separate quote lines.

Can I use this for a screed or slab?

Not for thickness. Here there are only m². Concrete volume has its own calculator.

A 5 cm screed on 20 m² is 1 m³ of material: switch to the concrete tool (or a screed mortar at the supplier). Floor covering is then laid on that area, with its own offcut margin.

Author and update

Written by Rédaction HexaCalc (editorial team). Content last updated: August 25, 2026. No third-party medical or financial review is claimed.

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