How the number is worked out
Area times depth gives cubic feet, divided by 27 gives cubic yards. The settling allowance is added to the total. The default 20% is extra loose volume for planning, not a measured shrinkage rate. Ask the supplier for the factor for your soil and placement. A 20% volume loss would require 25% extra loose material, not 20%. Set the allowance to zero if your quoted quantity already accounts for compaction.
area (ft²) × depth (ft) ÷ 27 × (1 + settling) = cubic yards
Fill dirt is not topsoil
Topsoil is the dark top layer with the organic matter that grass and roots need. Fill is what is under it. Fill is a third of the price and holds a shape; topsoil grows things. The usual job uses both: fill to bring the grade up to within 4 to 6 inches, then topsoil on top to seed or sod. Use the topsoil calculator for that last layer.
Screened or unscreened
Unscreened fill may contain rocks, roots and clods. Roots and organic debris can decay and leave voids, so do not assume excavation spoil is suitable structural fill. Screened fill spreads evenly; pay for it where the surface matters or where you will plant on top. Ask what the fill came out of: a clean basement dig is good fill, a demolition site is not.
Put it in in lifts
Spread it in layers rather than one heap, and firm each layer before the next goes on — how thick a layer and how damp depends on the soil and on what you have to compact it with, and a tamper does a job a truck tyre does not. For a wall, a foundation or anything that will carry weight, the drawings say how the fill goes in; follow them and have the compaction checked, because that is the one place the settling allowance cannot save you.
Typical jobs
| Job | Depth | Then |
|---|
| Filling a stump hole or old pool | to grade, in lifts | top 4 in with topsoil, seed |
| Raising a low lawn | to the planned subgrade | finish with 4 to 6 in topsoil; allowance is added by the calculator |
| Backfilling a wall or foundation | per project specification | use the specified soil, drainage and compaction |
| A shed or slab base | per project specification | use approved structural fill and the specified base |
Questions
How many yards of fill dirt are in a dump truck?
A single-axle truck carries about 10 cubic yards, a tandem 14 to 16. Fill is heavy — a yard weighs 2,400 pounds and more when wet — so the truck is usually limited by weight before volume.
Will fill dirt settle?
Loose fill can settle, but the amount depends on soil, moisture and compaction. The 20% default adds loose volume; it does not predict settlement. Confirm the allowance and placement requirements for your job.
Can I plant grass in fill dirt?
Not well. It has no organic matter and it packs hard. Bring the grade up with fill and finish with 4 to 6 inches of topsoil.
What about free fill?
Contractors give away excavation spoil to save the dump fee, and it is often perfectly good. Look at it before it arrives: you want soil, not concrete chunks, asphalt or rubbish.
Other calculators
The same ticket, the same assumptions on screen, for whatever else the job needs.
Concrete slabs, footings, columns and stepsGravel driveways, bases and drainage stoneRiver rock beds, borders and dry creeks, by stone sizeMulch beds and trees, by the yard or the bagAsphalt hot mix by the tonTopsoil beds, lawns and levellingCompost lawn top-dressing and bed amendingSand paver bedding, play sand and fillCubic yards any volume, in every unitRebar bars, sticks, laps and weight