Square Footage Calculator
Enter your shape and dimensions and we work out the area in square feet, square metres and square yards — and the total cost if you add a rate per ft².
Area (ft²)
120
- Area (m²)
- 11.15
- Area (yd²)
- 13.33
- Total cost
- £0.00
Rectangle: L × W. Triangle: ½ × base × height. Circle: π × (diameter/2)². Trapezoid: ½ × (b₁ + b₂) × h. Conversion uses 1 ft = 0.3048 m exactly (NIST), so 1 ft² = 0.09290304 m² and 1 yd² = 9 ft².
How to use this calculator
Pick the shape that matches the room or plot. For a rectangle or square, enter length and width. For a triangle, enter the base as "Length" and the perpendicular height. For a circle, enter the diameter as "Length" — width and height are ignored. For a trapezoid (a four-sided shape with two parallel sides — common for awkward rooms or plots), enter the two parallel sides as "Length" and "Width" and the perpendicular distance between them as "Height". Choose feet or metres for the input — output is given in ft², m² and yd² either way. Add a price per ft² (carpet, turf, paving, etc.) for an instant cost.
How the calculation works
A rectangle has area length × width. A triangle has area ½ × base × height. A circle has area π × r² where r is half the diameter. A trapezoid has area ½ × (b₁ + b₂) × h. The calculator runs the formula in whichever unit you chose, then converts. Conversions use 1 ft = 0.3048 m exactly (NIST SP 811), giving 1 ft² = 0.09290304 m² and 1 m² ≈ 10.7639 ft². 1 yd = 3 ft exactly, so 1 yd² = 9 ft² exactly.
Worked example
A 12 ft × 10 ft living room: 12 × 10 = 120 ft². In metric, 120 × 0.09290304 ≈ 11.15 m². In yards, 120 ÷ 9 ≈ 13.33 yd². At a flooring rate of £4.50 per ft², total cost = 120 × 4.50 = £540. For a circular patio 4 m across, π × 2² = 12.57 m² ≈ 135.3 ft². For a trapezoidal garden with parallel sides of 6 m and 4 m and a depth of 5 m, area = ½ × (6 + 4) × 5 = 25 m² ≈ 269.1 ft².
Frequently asked questions
How do I calculate square footage for an irregular room?
Break the floor plan into rectangles, triangles, and trapezoids — every room can be split into a few simple shapes. Calculate each piece, add them together, then add 5–10% for cuts and waste if you are buying flooring or paving. For very awkward rooms with curves, treat the curves as approximate rectangles or trapezoids; the small errors are absorbed by your wastage allowance. Don’t try to fit one formula to a complex shape — split first, then sum.
What is the difference between square footage and square metres?
They measure the same thing — flat area — in different units. 1 ft² = 0.09290304 m² exactly, because 1 ft = 0.3048 m exactly (NIST). So a 100 ft² room is about 9.29 m². A 10 m² room is about 107.6 ft². The conversion is exact, not approximate, when you use these factors. UK and EU markets typically quote m²; US markets quote ft²; real-estate listings vary, so always check which unit the price refers to before comparing.
Should I include built-in fixtures in the square footage?
For real-estate listings, the standard is to measure to the inside face of exterior walls and include the floor area under fixed cabinets, baths and stairs (because the floor area is still there). For flooring and carpet quotes, exclude the footprint of fixed cabinets, kitchen islands and chimney breasts — you don’t want to pay for material you can’t lay. The two figures will differ; use whichever matches the question you’re answering.
How accurate is the circle formula for a non-perfect circle?
The formula π × r² assumes a true circle. For a circular patio, pond, or rug that is roughly circular, take three or four diameter measurements through the centre at different angles, average them, and use the average. If the shape is more elliptical (longer in one direction), use π × a × b where a and b are the two semi-axes — that’s the ellipse formula. For very irregular curved shapes, approximate with a polygon.
How do I convert square footage to acres?
1 acre = 43,560 ft² exactly (US/UK statutory definition). So divide ft² by 43,560 to get acres: a 21,780 ft² plot is half an acre. In metric, 1 hectare = 10,000 m² and 1 acre ≈ 4,046.86 m². Most domestic plots are well under an acre, so it’s usually clearer to keep them in ft² or m². For larger land deals, switch to acres or hectares to keep the numbers readable.
Why is the price per ft² in pounds?
Calc Dragon’s default currency is GBP because the site originated in the UK, but the calculation is currency-agnostic — multiply the area in ft² by your local rate (per ft² or per m², adjusting accordingly) and the result is in your currency. Flooring, turf, paving and tiling are most often quoted per ft² in the US and per m² in the UK and EU, so check the unit the supplier is using before comparing.