Every drawing, order and bill on a site is a number with a unit. Structural drawings are dimensioned in millimetres, architectural plans often mix millimetres with feet-inches, sand and aggregate are ordered in cubic feet or brass, ready-mix concrete arrives in cubic metres, and steel is billed in kilograms and tonnes. Confusing any two of these is the most expensive reading mistake a trainee can make.
Learn the bridge conversions by heart: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 m = 3.28 ft, 1 m² = 10.76 sq ft, 1 m³ = 35.31 cft and 1 brass = 100 cft = 2.83 m³. A standard 9-inch wall is 230 mm, a 4.5-inch wall is 115 mm, and a 50 kg cement bag holds about 0.035 m³ (1.25 cft) of cement.
On the tape, read the exact edge, keep the blade straight and level, and always say the unit with the number. In records write 4,250 mm or 4.25 m — never a bare “4.25”. Before ordering, convert everything into the supplier's unit: m³ for ready-mix, cft or brass for sand, kg or tonnes for steel, bags for cement, and numbers for bricks and blocks.
1 inch / 1 foot
25.4 mm / 304.8 mm
1 m / 1 m²
3.28 ft / 10.76 sq ft
1 m³ / 1 brass
35.31 cft / 100 cft (2.83 m³)
Cement bag 50 kg
≈ 0.035 m³ (1.25 cft)
9 in / 4.5 in wall
230 mm / 115 mm
Remember on site
- Structural drawings are in millimetres unless noted otherwise — confirm before measuring.
- 1 ft = 304.8 mm · 1 m = 3.28 ft · 1 m³ = 35.31 cft · 1 brass = 100 cft.
- Always write the unit with the number; convert to the supplier's unit before ordering.
Check yourself
Structural drawings in India are normally dimensioned in which unit?
1 metre equals how many millimetres?
1 inch is exactly equal to…
1 foot equals…
A room measures 12 ft × 10 ft. Its area in square metres is closest to…
1 cubic metre equals approximately…
1 brass of sand equals…
A standard 9-inch brick wall is written on drawings as…
One 50 kg cement bag has a volume of about…
1 tonne equals…
On a metric measuring tape, the smallest marked division is…
A supplier quotes sand per brass but your estimate is 4.5 m³. How much do you order?