Area conversion happens in two dimensions
Area measures a surface, so both length dimensions must be converted. Because 1 ft = exactly 0.3048 m, one square foot is (0.3048 m) × (0.3048 m) = exactly 0.09290304 m². Multiplying a square-foot value by 0.3048 only once is a dimensional error.
The same rule applies at every scale. A square yard factor is the square of the yard factor, and a square-mile factor is the square of the mile factor. Volume extends the idea to three dimensions and requires a cubed length factor.
Choose a unit that fits the surface
Square centimetres and square inches suit small objects; square metres and square feet suit rooms, floors, and homes; hectares and acres suit land; square kilometres and square miles suit regions. A well-chosen unit keeps the number readable without changing the physical area.
- 1 square foot = exactly 0.09290304 square metre.
- 1 square metre ≈ 10.76391042 square feet.
- 1 hectare = exactly 10,000 square metres.
- 1 international acre = exactly 4,046.8564224 square metres.
- 1 square kilometre = 100 hectares.
Calculate the shape before converting
Measure every dimension in the same length unit, calculate the area, then convert the finished square unit. For a rectangle, use length × width. For a triangle, use base × perpendicular height ÷ 2. For a circle, use π × radius²; make sure the given dimension is a radius rather than a diameter.
For an L-shaped room, split the plan into non-overlapping rectangles, calculate each area, and add them. For a boundary with curves or many irregular sides, a survey, mapping tool, or coordinate-based calculation is more appropriate than a simple rectangle estimate.
Plan for waste and measurement uncertainty
A calculated surface area is not always the quantity to purchase. Flooring, tile, roofing, paint, and fabric may need an allowance for cuts, pattern matching, overlap, coats, or damaged material. Apply that project allowance after calculating the physical area and keep it clearly identified rather than silently changing the measurement.
Input precision still controls output precision. Dimensions rounded to the nearest centimetre cannot support an area reported to many decimal places. For property boundaries and legal descriptions, use the unit definitions and survey method required by the relevant jurisdiction.
- Sketch and label each dimension before calculating.
- Convert mixed length units before multiplying them.
- Keep square symbols—ft², m², km²—attached to results.
- Separate measured area from any purchasing or waste allowance.
Put this guide into practice
Convert a completed area—not a single side—and use the reverse tool as a quick check on your result.
- Square feet to square metres: Convert floor and property areas with the squared factor.
- Square metres to square feet: Reverse a room or plan conversion.
- Acres to hectares: Convert land area using the international acre.
- Hectares to acres: Compare metric and customary land areas.
Sources and standards
The definitions and factors in this guide were checked against these primary standards and government references.