Hong Life CalculatorsUnderstanding the size to weight calculator — concept and principle
This calculator works out the weight of a solid rectangular piece from its length, width and thickness and the material's density, for steel, aluminium, wood, concrete, glass, water and more. Makers, engineers and shippers use it to estimate lifting, shipping and structural loads.
How it is calculated
- Volume (m³) = length × width × height in cm ÷ 1,000,000.
- Weight (kg) = volume × density (kg/m³); lb = kg ÷ 0.45359237.
- Total = weight × number of pieces; litres = m³ × 1,000.
- Typical densities: water 1,000, ice 917, softwood C24 420, concrete about 2,400, glass 2,500, aluminium 2,700, structural steel 7,850, copper 8,960, lead 11,340 kg/m³.
The principle
Mass is volume times density. A solid box has volume length × width × height, so once the volume is in cubic metres, multiplying by the density in kilograms per cubic metre gives kilograms. The densities listed are typical values from European design standards and reference tables; timber varies with species and moisture, and concrete with its mix and reinforcement. For a hollow box, subtract the inner volume from the outer volume before multiplying.
Worked example
Default inputs: 100 × 50 × 1 cm, structural steel (7,850 kg/m³), 1 piece.
- Volume = 100 × 50 × 1 = 5,000 cm³ = 0.005 m³ = 5 litres.
- Weight = 0.005 × 7,850 = 39.25 kg.
- In pounds = 39.25 ÷ 0.4536 = 86.53 lb.
- Total for 1 piece = 39.25 kg; density used 7,850 kg/m³.
| Length (cm) | Weight of one piece (kg) |
|---|---|
| 25 | 9.81 |
| 50 | 19.63 |
| 75 | 29.44 |
| 100 | 39.25 |
| 125 | 49.06 |
| 150 | 58.88 |
| 200 | 78.5 |
How to read the result
Use the weight to plan lifting and transport: a 1 cm steel plate the size of a small table top is already about 40 kg. If precision matters, use the supplier's density or weigh a sample. Remember fixings, coatings and packaging add weight.
Common mistakes
- Mixing mm and cm when entering thickness.
- Using the density of solid material for hollow sections or tubes.
- Using a dry timber density for wet wood.
- Confusing kg/m³ with g/cm³ (1 g/cm³ = 1,000 kg/m³).
Frequently asked questions
How much does a 1 m × 0.5 m × 1 cm steel plate weigh?
About 39.25 kg at 7,850 kg/m³.
What is the density of steel?
7,850 kg/m³ for structural steel in EN 1993-1-1.
How do I find the weight of a hollow box?
Calculate the outer and inner volumes, subtract, then multiply by density.
Sources: EN 1993-1-1 (structural steel 7,850 kg/m³); EN 1999-1-1 (aluminium 2,700 kg/m³) · CRC Handbook of Chemistry and Physics (densities of water, ice, copper and lead)