Topsoil Calculator
Estimate topsoil volume, bags, and bulk cost. Enter area and depth, choose bag size and pricing, then get litres, kg, or cubic units fast.
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What the topsoil calculator does
Topping up a lawn or filling a bed takes a surprising amount of topsoil, and it is heavy and awkward to shift, so it is worth ordering the right amount once. This works it out. You give it the area and depth, and it returns the volume in your chosen unit, the weight in kilograms and pounds, the number of bags for your bag size, and a cost from either a bag price or a bulk price.
Below is how it gets there, the depths that suit different jobs, and how to decide between a bulk delivery and bags.
How to use it
- Enter the width, length, and depth. The area you are covering and how deep the topsoil goes, each with its own unit.
- Set your bag size and a price per bag if you are buying bagged, or a price per tonne for a bulk delivery.
- Pick the output volume unit, then press Calculate for the breakdown, or Reset to clear it.
How the volume, weight, and bags are worked out
The volume is the area times the depth:
Volume = width × length × depth
From that volume the calculator works out the weight, using a topsoil density of about 1,600 kilograms per cubic metre, since bulk topsoil is often priced by the tonne. For the bag count it divides the volume by the size of one bag, so you can see how many of your chosen bags it takes. The two together let you compare buying bagged against a bulk load.
How deep to lay topsoil
The depth drives the whole order, and it depends on the job. A light topdressing over an existing lawn is thin, around half an inch to an inch. Laying soil for new grass seed wants more, about 4 to 6 inches of good soil for the roots. Flower beds sit deeper again, often 6 to 8 inches, and vegetable beds deeper still at 8 to 12 inches so roots have room to run.
Topsoil settles after it is spread and watered, dropping a little from its loose depth, so it is worth being slightly generous rather than measuring it tight.
A worked example: a 10 ft by 10 ft bed
Say you are filling a 10 foot by 10 foot bed to a depth of 6 inches.
That works out to about 50 cubic feet, or 1.85 cubic yards, weighing roughly 2,270 kilograms, which is around 5,000 pounds. In bags of 1.5 cubic feet each, that is about 34 bags.
It is a good illustration of the weight catching people out: a fairly modest bed is well over two tonnes of soil to move, which is why a bulk delivery often wins for anything this size.
What topsoil weighs, and why it varies
Topsoil does not have one fixed weight. It changes with how wet it is and how much it has been screened, so a damp, dense load weighs more than a dry, fluffy one for the same volume. The calculator uses a typical figure of about 1,600 kilograms per cubic metre, which sits on the heavier, moister side of the range. Screened, drier topsoil can weigh a fair bit less.
So treat the weight as a solid estimate for ordering and for working out whether your trailer can carry it, rather than an exact figure. If your supplier quotes a density of their own, theirs will be closer for that particular soil.
Bulk or bags
Bags suit small jobs and topdressing, where they are easy to carry and you only open what you need. A bulk delivery, sold by the tonne or the yard, is cheaper per unit and far less lifting for a lawn or a big bed, provided you have somewhere for the pile to sit.
Whichever you choose, add a little to the figure for settling and spread, and round the bags up. Coming up short across a lawn is a visible, patchy thing to put right after the fact.
Questions people ask
How much topsoil do I need?
Multiply the area by the depth for the volume. A 10 by 10 foot bed at 6 inches deep comes to about 1.85 cubic yards, or roughly 50 cubic feet.
How much does a yard of topsoil weigh?
Usually somewhere around 1.1 to 1.5 tons, depending on moisture and how much it has been screened. Damp, unscreened soil sits at the heavier end.
How deep should topsoil be for a new lawn?
About 4 to 6 inches of good soil gives grass roots enough to establish in. A topdressing over an existing lawn needs only half an inch to an inch.
How much area does a yard of topsoil cover?
About 108 square feet at 3 inches deep, or 54 square feet at 6 inches. The deeper the layer, the less ground a yard covers.
References
A quick note on where these figures come from. The volume is pure geometry, the area times the depth. The weight rests on the bulk density of soil, which varies with moisture and organic content, and the calculator uses a typical value of about 1,600 kilograms per cubic metre; soil bulk density and its variation are documented by the US Department of Agriculture's Natural Resources Conservation Service. The unit conversions follow the US National Institute of Standards and Technology guide.
- US Department of Agriculture, Natural Resources Conservation Service, Soil Survey and soil properties (bulk density). https://www.nrcs.usda.gov/resources/guides-and-instructions/soil-survey
- National Institute of Standards and Technology (NIST), Special Publication 811, Guide for the Use of the International System of Units (SI). https://www.nist.gov/pml/special-publication-811
Mahendra Thapaliya is a graduate student in Structural Engineering at the University of Bologna, with research interests in structural systems, FEM, earthquake engineering, and numerical modeling. At Eon Tools, he reviews construction tools.