How Much Topsoil Do You Need?

Sketch each bed as a rectangle or use length × average width on a curve. Skip patio slabs and paths you will not cover. If beds wrap a house, measure along the foundation and out to the bed edge in a few places, then average the depth of the bed strip.

Lawn topdressing is different: you are covering most of the grass area, so measure the lawn the way you would measure a room — length × width, or split L-shapes into rectangles and add them.

Odd shapes are fine. Split once, run the Topsoil Calculator twice, and add the volumes. Guessing “a couple of yards” is how you finish a corner with dusty subsoil showing through.

New planting beds commonly get about 4–6 inches (10–15 cm) of decent topsoil over loosened subgrade. Going from 4 to 6 inches is a 50% jump in volume for the same footprint — that shows up on the ticket fast.

Lawn topdressing is thinner. A half-inch to one inch of screened mix is typical for evening low spots and feeding the root zone without burying the grass. Dumping four inches of topsoil on an existing lawn is a different project (and usually a bad one).

Raised beds are taller by design. If the box is 12 inches deep and you are filling it, calculate that full depth — or blend topsoil with compost per your planting plan. The calculator does not invent your mix ratio; it only does area × depth.

Suppliers talk in cubic yards or cubic metres. Your tape measure gives feet or metres and inches or centimetres. Convert depth to the same unit as length and width, multiply, then convert: cubic feet ÷ 27 = cubic yards.

Weight is a booking hint for the truck, not a promise. Moist clay weighs more than dry sandy loam. The Topsoil Calculator shows an approximate tonnage using a mid-range density so you can ask for “about X yards / Y tons” without sounding lost — then order against the yard’s product chart.

Worked check: a 20 × 10 ft bed at 4 inches is about 2.5 yd³ before waste. Add 10% and you are in the high-2s / low-3s. That is already a small bulk load for many yards, not a wagon of bags.

Soil settles. Grades are never as flat as the sketch. A 5–10% buffer is normal for a simple rectangle. Soft spots you dig out and refill need more. Skip the buffer only if you enjoy a mid-project run to the yard.

If you are blending compost on site, decide whether the calculator depth is finished topsoil only or the whole blend. Mixing 30% compost by volume changes how many yards of each material you buy — do that math on paper, not in your head at the till.

Bagged “garden soil” is fine for a single shrub hole or a tiny border refresh. Once you need more than roughly a cubic yard, bulk screened topsoil almost always wins on price if a truck can tip near the bed.

Check access. A tipper that cannot reach the back garden means wheelbarrow labour that can cost more than the soil. Ask about minimum load fees — a “half yard” on the phone sometimes still bills like a full small load.

Fill dirt raises grade. It is cheaper and usually lifeless for planting. Topsoil has organic matter plants actually use. If someone quotes a rock-bottom “soil” price, ask which one they mean.

Screened topsoil costs more and spreads cleaner. Unscreened loads may include rocks and clods you will pick out by hand. For lawn topdressing, screened material saves grief.

Run the Topsoil Calculator with your real length, width, and depth, then call two local yards with the volume in hand. Ask product name, screened or not, and whether the price is per yard or per tonne.

Plan mulch separately. Bark on top of a new bed is a different calculator and a different delivery. Use the Mulch Calculator once the soil is in and graded.

If you are building a patio base under the soil work, gravel and sand layers are not topsoil — keep those takeoffs on the Gravel and Sand calculators so the tickets stay honest.