Area squares the unit
Converting feet to meters is linear, but converting square feet to square meters requires the squared conversion factor. This is why area conversions can surprise people.
Use area units for flooring, walls, land, paint coverage, and screen size comparisons. Do not mix them with linear measurements.
Volume cubes the unit
Volume conversions grow even faster because the unit is cubed. Cubic feet, cubic meters, litres, gallons, and millilitres describe capacity, not length.
For storage boxes and tanks, calculate internal dimensions when usable capacity matters. Outer dimensions can overstate how much space is actually available.
Add waste and tolerance
Material estimates should include waste for cuts, spills, uneven surfaces, and measurement error.
For expensive or safety-critical projects, confirm measurements with a qualified supplier or professional before ordering.