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The dimensions and weights used in this booklet are all given in metric measurements.


This is how to convert inches, feet and yards into metres:

Multiply by to obtain
Inches 0.0254 Metres
Feet 0.3048 Metres
Yards 0.9144 Metres
Metres 39.3701 Inches
Metres 3.2808 Feet
Metres 1.0936 Yards


The basic metric unit for volume is the cubic metre which is made up of 1 000 litres. The cubic metre is abbreviated in the form m3.
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This is how to convert gallons into litres and cubic metres:

Multiply by to obtain
Gallons 4.5460 Litres
Gallons 0.0046 Cubic metres
Litres 0.2200 Gallons
Litres 0.0010 Cubic metres


Areas of land are usually measured in local units, which differ from country to country.

In engineering, however, the metric unit of measurement is the square metre (m2). Large areas are measured in hectares (ha) and vast expanses in square kilometres (km2).

1 hectare = 10 000 square metres
1 square kilometre = 100 hectares

This is how to convert square feet, square yards and acres into square metres:

Multiply by to obtain
Square feett 0.03010 Square metres
Square yards 0.8361 Square metres
Acres 4 046.86 Square metres
Square metres 1.1960 Square yards
Hectares 11 960.0 Square yards


This is how to convert ounces and pounds into grams, kilograms and tonnes:

Multiply by to obtain
Ounces 28.3495 Grams
Ounces 0.0283 Kilograms
Pounds 0.4536 Kilograms
Tonnes 2204.62 Pounds
Kilograms 2.2046 Pounds

Some useful weights
It is useful to know that:

Aggregate made from crushed coral weighs much less depending on the porosity of the coral.

Concrete. 1 m3 of concrete made with normal aggregates weighs about 2 300 kg. Concrete made with coral aggregate may weigh as little as 1 500 kg per m3.

However, 1 m3 of normal concrete immersed in sea water has an effective weight of less than 2 300 kg. This is caused by the uplift of the salt-water and should be borne in mind when casting anchor blocks for vessels. For example, the submerged weight of a concrete anchor block measuring 400 mm x 400 mm x 300 mm can be calculated as follows:

Hence, although the 110-kg anchor block is heavy to handle, it only provides 61 kg of pull when placed in water and may drag along the bottom during rough weather.

Timber. The weight of timber varies according to the species of tree. Here are some examples:

As these weights show, both greenheart and ironbark weigh more than sea water and, so, do not float.

Metals. The weight of a sheet of the following metals, 1 m2 x 1 mm thick (that is a volume of 0.001 m3), can be expressed as follows:

Aluminium weighs 2.56 kg
Zinc weighs 7.20 kg
Steel weighs 7.80 kg
Brass weighs 8.55 kg
Copper weighs 8.90 kg
Lead weighs 11.37 kg


Civil engineering, like other branches of engineering, follows preset rules of presentation in order that drawings and plans can be easily read and understood.

Dimensions. On normal drawings, dimensions up to 10 m are usually expressed in millimetres. Over 10 m, dimensions may be expressed directly in metres. Diameters are usually expressed in millimetres; a 100-mm diameter pile is expressed as "Ø100".

Levels. Levels above and below mean sea level are usually expressed in metres up to two decimal places. A quay 1.5 m above sea level is said to be at +1.50 m. Similarly, a sounding that is 2 m deep is expressed as -2.00 m. When there are tides, which change the depth of the water, all levels should refer to chart datum or low water spring level (LWS) (see Figure 22).

Symbols. The symbols for sand, rock, etc., used in this booklet are internationally recognized symbols (Figure 105).


All drawings, apart from sketches, are drawn to a scale (Figure 106).
Drawing scales are necessary to represent actual construction dimensions on paper.
A scale of 1 to 50 or 1:50, means that a length that is 20 mm on the drawing represents 50 time 20 mm, that is 1 m, in real life.
Moving to a smaller scale of 1:100 (the scale 1:50 is twice as big as the scale 1:100), a length of only 10 mm represents 1 m.


Similarly, on an even smaller scale of 1:200, 5 mm represents 1 m.

What scale and size of paper should be used? The international printing paper A-series is a very common standard and should be used:

A1-size is 841 mm long and 594 mm wide.
A3-size is 420 mm long and 297 mm wide.

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Layout drawings of shelters or harbours should be as big as possible. For example, a stretch of coast 168.2 m long will just fit on to an A1-size paper (841 mm long) if it is drawn at a scale of 1:200 (200 x 841 mm = 168.2 m). If a scale twice as big, 1:100, is used only half the above length, or about 84 metres, would fit on to the same piece of paper.
Construction details, such as cross-sections, require a scale no bigger than 1:50, preferably 1:20.

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