Calculation for mould volume
Measure the inner dimensions of the mould and calculate. Add a little extra for hang-up. Keep records so that wastage can be kept to a minimum.
Always take care to use the same units in a calculation. It is often easier to change them all to the same unit before starting.
Volume of a block : Length x width x height
Therefore if the container is 4m long, 2m wide and 3m high, the volume is 4x3x2 = 24 cubic metres
Volume of a cylinder : area of circle x length (or height) of cylinder
Area of a circle = pi x radius x radius
(radius = half the diameter)
(pi = 3.1415927)
Therefore the volume of the cylinder:
= Pi x radius x radius x length
= 3.1415927 x 4 x 4 x 14
= 703.7
Volume of a cone : One third x volume of a cylinder
Volume of a cone : Pi x radius x radius x height x one third
Height = 47.75 dm
Diameter = 4 dm
Radius = 2 dm
Therefore volume is : pi x radius squared x height x one third
Pi x 2 x 2 x 47.75 x 1/3
= 200 cubic decimetres (dm3)
Volume of pipe walls or wheels:
A pipe consists of two cylinders, mathematically speaking.
Measure both the ID and the OD (internal and external diameter).
Calculate the volume twice, once based on ID, once based on OD.
Subtract the smaller figure from the larger figure.
This gives the volume of the walls of the pipe.
(pi = 3.1415927)
Example:
ID = 4.5 cm (RADIUS = 2.25 cm)
OD = 5 cm (RADIUS = 2.5 cm)
LENGTH = 200 cm
Calculation:
(pi x 2.5 x 2.5 x 200) – (pi x 2.25 x 2.25 x 200)
= 3 926.99 - 3 180.86
= 746.13 cm3
= 746.13 ml
Measurement Conversions
If linear measurements are in decimetres, volume is in litres.
For practical purposes: 1 dm3 = 1 litre
If SG = 1: 1 litre = 1 Kg
If linear measurements are in centimetres, volume is in millilitres
For practical purposes: 1 cm3 = 1 ml
If SG = 1: 1 ml = 1 g
Other methods of estimating volume :
- Weigh the mould
- Fill with water
- Weigh the mould again
- Subtract the smaller figure from the larger
- This gives the mould volume.
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