About the Flooring Calculator
Most modern flooring — engineered wood, solid wood, luxury vinyl plank, rigid core and laminate — is sold in boxes, and each box states how much floor it covers. So working out how much to buy is a matter of measuring the floor, adding a waste allowance, and dividing by the coverage per box.
What makes the difference between enough and not quite enough is the waste allowance. Every row ends with a cut board, doorways and radiator pipes need notches, and patterned layouts such as diagonal or herringbone cut far more. The right allowance depends on the pattern and the shape of the room.
This flooring calculator measures one or two rectangles — so it handles L-shaped rooms — adds waste for the laying pattern, and tells you how many boxes to buy, how much spare they leave, and how many rolls of underlay you need.
How to Use the Flooring Calculator
Choose metres or feet.
Enter the room's length and width. For an L-shaped room, enter the second rectangle's length and width as well.
Choose the pattern: straight, diagonal or herringbone. The waste allowance defaults to suit it.
Enter the coverage per box from the packaging — in square metres or square feet.
Optionally, enter the underlay roll coverage to count rolls.
How the Boxes Are Worked Out
floor area = length × width (+ second area)
to buy = floor area × (1 + waste %)
boxes = to buy ÷ coverage per box, rounded up
underlay = floor area × 1.05 ÷ roll coverage, rounded upStep-by-Step Example
A 5 × 4 m room, straight lay, 2.22 m² per box, underlay in 15 m² rolls.
Floor area: 5 × 4 = 20.00 m²
With 8% waste: 20 × 1.08 = 21.60 m²
Boxes: 21.60 ÷ 2.22 = 9.7 → 10 boxes
Underlay: 20 × 1.05 ÷ 15 = 1.4 → 2 rollsTen boxes cover 22.2 m², leaving about 2.2 m² of boards spare after fitting — useful for future repairs.
Waste by Pattern
Straight lay — boards run parallel to one wall, with a cut at the end of each row. The offcut from one row usually starts the next, so waste is low: about 5 to 10%. The calculator defaults to 8%.
Diagonal — boards run at 45° to the walls, so every board touching a wall is cut at an angle, and those offcuts are rarely reusable: about 15%.
Herringbone and chevron — short blocks in a zigzag, with every edge block cut to an angle and careful alignment needed through the middle of the room: about 20%.
Rooms with bay windows, fireplaces, pillars, many doorways or awkward alcoves need more than these figures.
Measuring L-Shaped and Irregular Rooms
The simplest way to measure a room that is not a rectangle is to split it into rectangles, measure each, and add the areas together. An L-shaped room is two rectangles, which the calculator takes directly. For more complex shapes, sketch the floor, divide it into as many rectangles as needed, add their areas, and enter the total as a single length and width (for example, the total area as the length and 1 as the width).
Include cupboards and alcoves that will be floored, and measure into doorways to the point where the new floor will meet the next.
Underlay and Preparation
Floating floors — laminate, many engineered boards and rigid-core vinyl — sit on an underlay, which evens out minor bumps, reduces footstep noise and, over concrete, may include a damp-proof layer. Underlay is laid across the whole floor with small overlaps or taped joins, so it needs only about 5% extra. Some products come with underlay attached, in which case none is needed.
The floor underneath should be flat, clean and dry. Most manufacturers specify a maximum unevenness, often around 2 to 3 mm over a metre, and high spots need sanding or low spots filling first.
Acclimatisation and Expansion Gaps
Wood and wood-based flooring move with temperature and humidity. Leave the boxes flat in the room for about 48 hours before fitting so the boards adjust to its conditions. Always leave the expansion gap the manufacturer specifies around the edges of the room, hidden later by skirting or beading; floors fitted tight to the walls can buckle when they expand.
Doorways, Thresholds and Trims
Where the new floor meets another room, it needs a threshold strip or transition profile to cover the expansion gap and handle any change in height. Measure each doorway and buy one profile per opening.
Around the walls, the expansion gap is hidden by skirting boards, or by a scotia or beading fixed to existing skirting. Measure the room's perimeter, less door openings, to work out how much trim you need; the baseboard calculator does this.
Door frames and architraves are best undercut with a flush saw so the boards can slide underneath, which looks neater than scribing around the frame and leaves the expansion gap hidden.
Understanding Your Result
Boxes needed is the number of boxes including waste.
Area shows the floor area and the area with waste.
What the boxes cover shows the total coverage and the spare.
Underlay gives the number of rolls.
Worth knowing covers acclimatisation and expansion gaps.
When Should You Use This Calculator?
Before buying flooring, to order enough boxes from one batch.
For L-shaped rooms and open-plan spaces.
When choosing a pattern, to see how herringbone changes the count.
Pricing a job, with underlay and trims.
Common Mistakes
Ignoring the pattern. Herringbone needs far more than straight.
Forgetting cupboards and alcoves.
Skipping acclimatisation. Boards move after fitting.
Fitting tight to the walls. Leave the expansion gap.
Buying exactly enough. Keep spare boards for repairs.