The Green Gardener
Working out how much topsoil you need.
Working out how much topsoil you need can be a bit of a daunting task, is it just a case of guessing? Most people do just guess and often get it wrong!
Follow our guide below to hopefully eliminate the guess work and save you alot of hassel and money.
Topsoil is usually sold in tonnes, but for now we are going to forget about weight and concentrate on volume.
Step 1 - Measure the Length & Width of the Area
Firstly, work out the area you want to cover with topsoil in metres by measuring the length and width of the flower bed, planter or new lawn that you want to fill with soil. For example of you have a planter that is 200cm long by 50cm wide = 2m x 0.5m which = 1 metre squared (m²).
Step 2 - Measure the Depth
Next meaure the depth of the area that you want to fill with soil or the height of the planter you want to fill. i.e 10cm depth = 0.1m or 5cm depth = 0.05m.
At this point you have two options: Option 1) Use a Topsoil Calculator to work out the amount in tonnes you need (skip steps 3 & 4) or go to Step 3.
Step 3 - Work out the volume
Next multiply the area from step 1 by the depth from step two:
e.g. you are trying to work out how much topsoil you need for an area that needs topping up with soil before laying new turf:
You have meaured the length at 10m and the width is 6.35m (635cm).
You want to increase the height of the area by 5cm (0.05m).
So simply multiply the length by the width by the depth (all in metres) i.e 10m x 6.35m x 0.05m = 3.175 cubic metres (m³).
This gives you the volume of the area you wish to fill with soil in cubic metres (m³).
Step 4 - Convert the volume in cubic metres to tonnes
Convert the volume in cubic metres to tonnes by multipling the volume by the bulk density of topsoil.
As a general rule there is about 1.4 tonnes of topsoil to the cubic metre, therefore multiply the volume (as calculated above) by 1.4
i.e 3.175m³ x 1.4 = 4.45 tonnes
For more information on topsoil visit our specialist topsoil site here.