Floor Area Calculator
Calculate floor area in square metres from length and width, with optional quantity for repeated identical spaces.
Use calculator →Measuring & Conversion Calculators — Area, Volume & Units
Free UK measuring and conversion calculators for floor area, wall area, cubic metres, linear metres, length units, area units and room volume.
Wall Area Calculator
Calculate gross and net wall area from room perimeter, wall height and total openings.
Use calculator →Cubic Metre Calculator
Calculate cubic metres and litres from three dimensions entered in metres.
Use calculator →Linear Metre Calculator
Convert an area requirement into linear metres for material of a fixed cover width.
Use calculator →Length Converter
Convert millimetres, centimetres, metres, inches and feet for UK site measurements.
Use calculator →Area Converter
Convert square metres to square feet, square yards and acres.
Use calculator →Room Volume Calculator
Calculate room volume in cubic metres, litres and cubic feet from length, width and height.
Use calculator →Which measuring calculator should you use?
Area
Use the Floor Area Calculator for floors and rooms, or the Wall Area Calculator when you need wall surface area with doors and windows deducted.
Volume
Use the Cubic Metre Calculator for general rectangular volumes, or the Room Volume Calculator for internal room dimensions and air-space volume.
Conversions
Use the Length Converter for mm, cm, m, inches and feet, or the Area Converter for m², ft², yd² and acres.
A simple measurement workflow
Reliable quantity estimates usually start with the same sequence: measure the real dimensions → keep the raw measurements → convert units before multiplying → calculate area or volume → move into the material-specific calculator. This keeps geometry separate from coverage, density, waste and purchasing assumptions.
Length, area and volume are different quantities
- Length uses units such as mm, cm, m, inches and feet.
- Area uses square units such as m², ft² and yd².
- Volume uses cubic units such as m³ and ft³.
- Linear metres describe run length and need a known cover width when converting from area.
Confusing these measurement types is one of the easiest ways to create a large estimating error. The Builder’s Measurement Checklist gives a fuller site-measuring workflow.
Measurement rule
Preserve the original dimensions, convert into compatible units before calculating, and treat the measured geometry as separate from product coverage, waste, density or pack size.
How to use the Measuring & Conversion calculators accurately
These tools are designed to feed the wider Builder’s Toolkit calculators with clean geometry and unit conversions. A simple formula with correct units is more useful than a complicated formula built on inconsistent measurements.
Four checks that improve the estimate
- Record the raw dimensions before converting them.
- Convert all inputs into compatible units before multiplying or dividing.
- Keep length, area and volume units distinct.
- Delay rounding until the final useful result where practical.
Once the geometry is correct, use the relevant material calculator so coverage, density, spacing, waste and pack rounding remain visible assumptions rather than being hidden inside the measurement step.
Useful measuring guides and references
For more detail, use the How to Calculate Square Metres, How to Calculate Cubic Metres, Measuring Walls & Openings and Builder’s Measurement Checklist guides.
Frequently asked measuring questions
How do I calculate square metres?
For a rectangle, multiply length by width with both measurements in metres. Split irregular shapes into smaller rectangles and add the areas.
How do I calculate cubic metres?
Multiply length by width by depth or height, with all three measurements in metres.
How do I convert millimetres to metres?
Divide millimetres by 1,000. For example, 100 mm = 0.1 m.
Can square metres be converted directly to linear metres?
Only when you also know the effective material cover width. Divide area in m² by cover width in metres.