How to use the flooring calculator
- Choose feet or metres, then add each room. Split an L-shaped room into two rectangles.
- Enter the total width of door openings in each room so no trim is counted across doorways.
- Pick a laying pattern to load a suggested waste allowance, or type your own.
- Enter the coverage per box and the price per box or per unit area.
- Optionally add underlayment and trim, then review boxes, cost and the room table.
Worked example
12 × 10 ft bedroom plus a 14 × 12 ft living room with a 6 × 5 ft extension
Area 120 + 168 + 30 = 318 sq ft; with 10% waste 349.8 sq ft. At 20 sq ft per box that is 17.49, rounded up to 18 boxes (360 sq ft). At an example $4 per sq ft ($80 per box) the flooring costs $1,440. Perimeter 44 + 62 = 106 ft minus 6 ft of doors = 100 ft of trim; with 10% waste and 8 ft pieces, 14 pieces. Underlayment at 100 sq ft per roll: 4 rolls. Total materials $1,700 at the example prices.
How it works
Area = Σ (l1 × w1 + l2 × w2 for L-shapes). Boxes = ⌈area × (1 + waste) ÷ box coverage⌉. Cost = boxes × price per box (price per area × box coverage when priced by area). Perimeter of an L made of two rectangles joined along the first one’s length = 2 × (max(l1, l2) + w1 + w2). Trim = perimeter − door widths; pieces = ⌈trim × (1 + trim waste) ÷ piece length⌉. Underlayment rolls = ⌈area ÷ roll coverage⌉.
Assumptions
- Pattern waste suggestions (straight 10%, diagonal 15%, herringbone 20%) are rule-of-thumb starting points, editable, and not manufacturer requirements.
- Box coverage, prices, underlayment coverage and trim piece length are yours to enter; starting values are examples.
- L-shaped rooms assume the second rectangle sits along the first rectangle’s length side.
- Underlayment is based on floor area without waste or overlap.
Frequently asked questions
How much extra flooring should I buy?
It depends on the product, pattern and room shape. Diagonal and herringbone layouts create more offcuts than straight lays. Follow the manufacturer’s guidance and consider keeping a spare box for repairs.
How do I measure an irregular room?
Split it into rectangles. Use an L-shape for two, or add extra rooms for more pieces. Closets can be added as small rooms with no door width.
Why subtract door widths from trim?
Skirting or quarter-round is not installed across doorways, so counting it there overstates what you need.
Limitations
- Does not plan plank layout or tile cuts.
- Perimeter for complex shapes built from several rooms counts shared walls twice; adjust door widths if needed.