https://todaysgardens.org/topsoil-calculator/Planning estimate — generated in your browser and not stored.
How much topsoil you need is the area you are covering multiplied by the depth you intend to lay, plus whatever overage you decide to allow. This tool does that arithmetic and shows it: it does not assume a density, a bag size or a bulk bag size for you.
Your estimate
Worked example — not your result
A 10 m × 5 m lawn at 100 mm depth, with 5% overage, 60 L bags, 0.6 m³ bulk bags and a supplier density of 1200 kg/m³.
5.00 cubic metres (m³)
Litres
5,000 L
Measured area
50.00 m²
Gross volume after 5 % overage
5.25 m³
Bags at 60 L
88
Bulk bags at 0.6 m³
9
Weight at 1200 kg/m³
6.30 t
Assumptions in this example
Depth
100 mm
Overage
5 %
Bag size
60 L
Bulk bag size
0.6 m³
Density
1200 kg/m³
This is an example, not your result. It matches golden vector V1–V5 in the
calculation methodology. Enter your own measurements and select
Calculate.
How much topsoil do I need?
Multiply the area you are covering by the depth you intend to lay, then add whatever
overage you want to carry. A 10 m × 5 m lawn at 100 mm is 5 m³, which is 5,000 litres. At
the same area and 50 mm it is 2.5 m³. Depth is doing most of the work in that sum, which
is why it is worth deciding deliberately rather than accepting a default.
The awkward part is not the arithmetic, it is the units the material is sold in. Bagged
topsoil is sold in litres, bulk bags in cubic metres, and loose loads by weight. This tool
will convert to all three, but only from sizes and a density you enter, because those
figures differ between suppliers and the wrong one produces a confidently wrong order.
How much topsoil for turf?
This is the question the topping-up mode exists for, and it deserves an honest answer: the
guidance this site cites does not give a topsoil depth for turfing. What it gives is a
cultivation depth — dig or rotavate the existing soil to 20–25 cm so there is no
compaction, and work in well-rotted organic matter. Whether you then need to import
topsoil, and how deep, depends on how much usable soil you already have and how far the
level is short.
In practice: if you are correcting a level, measure how deep the shortfall actually is and
use that. If you are improving a thin soil, the depth is a judgement about what the grass
needs to root into. Either way it is a decision about your ground, and the tool will not
pretend to make it for you. The
ground preparation planner sets out the whole
sequence in order.
Topsoil depth for turf, and other depths people ask about
Depths are a decision, not a constant, and the honest position is that this site publishes
no depth of its own. What it can do is make the consequence of your decision visible
immediately: change the depth and the volume, the bag count and the tonnage all move
together in the same render, with the depth you chose echoed beside them.
Ordering against this figure
Two things reliably catch people out. The first is delivery access: a bulk bag needs a hard,
level surface within reach of a tail lift, and a loose load needs somewhere to tip. The
second is minimum loads — below a certain volume many suppliers price a part load as a full
one, which can make a slightly larger order cheaper per cubic metre.
How this figure is worked out
Every step is arithmetic you can repeat by hand. Full precision is kept through the
calculation and rounded once for display.
Formulae used on this page
Step
Formula
Depth to metres
depth m = mm ÷ 1000, or cm ÷ 100, or m × 1
Cubic metres to litres
1 m³ = 1000 L
Net volume
net volume m³ = net area m² × depth m
Gross volume after overage
gross volume = net volume × (1 + overage % ÷ 100)
Bag count
bags = ceiling(gross litres ÷ bag litres)
Bulk bag count
bulk bags = ceiling(gross m³ ÷ bulk bag m³)
Mass from a density you entered
kg = gross m³ × density kg/m³, and tonnes = kg ÷ 1000
Complete the site preparation well before buying or having the turf delivered.
Get rid of perennial weeds such as couch grass and bindweed first, forking out the roots.
Dig or rotovate the soil to a depth of 20–25cm so there is no compaction.
Incorporate plenty of well-rotted manure or other organic matter, especially on sandy soil — and only well-rotted material, because undecomposed matter shrinks and makes the surface sink unevenly.
Measure the area and check the dimensions of the turf pieces carefully before buying.
Lay turf within 24 hours of delivery if possible; if laying is delayed more than a few days, unroll it flat and water it if dry.
Stand on boards to avoid making footprints, stagger the joints like bricks in a wall, and push the pieces together tightly.
Turf is best laid in mid-autumn and can be laid from mid-autumn to early spring whenever the soil is not too wet or frosty; laying from mid-spring to early autumn is best avoided.