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How to calculate volume or cubic meters (m3)

In many cases we need to order or get delivered some materials to our home or to our work site, some materials used that may need to be calculated are, concrete, garden mix, mulch, topsoil, sand, compost, manure, road base, pine bark, garden chips, saw dust, aggregate, pebbles or clean fill.

 Guestimates could potentially cost you a lot of money

Say you need to calculate concrete for a garden shed slab floor, you multiply width by length by depth.

For example; Your shed is 2.0 wide by 2.0 long and you want the concrete to be 100mm thick

The formula to calculate the volume of concrete that you need to order is this,

2.0×2.0×0.1 = 0.4m3

 NOTE; as in most estimates, it would be wise to add an additional 10% for wastage or for inconsistencies within your project ( length x width x depth + 10%)

2.0×2.0×0.1 + 10% = 0.44m3

TO ESTIMATE DRY, PRE MIXED, BAGGED CONCRETE

Each 20kg bag produces approx 10litres of concrete.

1×20kg bag = 0.01m3

99×20kg bag = 1.0m3

TO ESTIMATE, BAGGED MATERIAL, SOIL, COMPOST OR BARK CHIPS

1000 litres make up 1m3. To work out how many 50ltr bags of compost will fill 1 cubic meter, divide 1000 by the size of the bag.

1000L/ 50L = 20 bags

1000L / 25L = 40bags

ESTIMATE COMPRESSED MATERIALS SUCH AS ROAD BASE

To do this we times total volume by 1.5

2.0×2.0×0.1 + 10% = 0.44×1.5 = 0.66m2 

If you want to calculate different or odd shaped areas, break the project down to manageable sizes to calculate.

To calculate different materials in volume, its the same as above, for instance mulch, your garden is 15m x 1m and you would like 10mm of mulch, following the same formula as above.

15.0×1.0×0.1 + 10% = 3.15m3

To calculate the volume required within a circle

To calculate the volume within a circle, the formula we use is 3.1415 x radius x radius x depth

The radius of a circle is half of its diameter.

The radius is from the centre of the circle to the outside edge, the diameter of a circle is from the out side edge through the centre point to the other side.

 To calculate, say your garden bed is 5m in diameter that means that the radius is 2.5m, so weather you would like to fill this area with soil or with mulch we follow the simple formula above.

For soil; 3.1415×2.5×2.5×0.6 + 10% = 13.9m3 or round up to 14

For Mulch: 3.1415×2.5 × 2.5×0.1 +10% = 2.16m3

Alternative

Call your concrete or landscape supplier and give them your square meter (m2) measurements and they will work out exactly how many cubic meters (m3) you need for your projects.