Dirt Calculator: What the Low Corner Actually Takes
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The decision that comes before any measuring is which material the hole wants. Structural fill and growing soil are two different orders with two different weights, and on a Maryland lot the line between them usually sits four to six inches below the finished grade. The dirt calculator sizes the part underneath: the subsoil that carries load, closes a trench and lifts a low corner out of standing water. Everything that has to grow goes on top of it afterwards, as its own calculation.
How much ground does a settled corner actually cover?
Pace it, then measure it. A dip in a lawn has no edge to work from, so walk out to where the ground stops falling away and put stakes at the four corners of a rectangle that contains the whole thing. Length and width go into the form in feet.
Rectangle mode handles most of it. Multiple areas takes up to five at once, which is the setting for a yard with a low corner, a settled path and a trench all going in the same week. Circle mode wants the diameter straight across, which is the one to use for a filled-in pond or a removed tree pit.
For an example, take a soft corner of lawn 17 by 12 feet. That is 204 square feet before any depth is decided.
The hole is deeper at one end. What depth do I type?
An average, and you get it by measuring both ends. Lay a board or a string line across the dip at the level you want the finished grade to sit, then measure down to the ground at the deepest point and at the shallow edge. The midpoint of those two is the number that goes in the depth box.
Depth is entered in inches, anywhere from 0.25 to 24. That ceiling matters more here than on any other material page, because holes go deeper than two feet and fill is the thing that closes them. Split anything deeper into layers and run it twice.
Working the example through: the corner measures 7 inches down at the worst point and 3 at the edge, so 5 inches goes in the box. Five inches is 0.4167 of a foot, so 204 square feet of ground gives 85 cubic feet. Divide that by 27 and the corner takes 3.15 cubic yards.
A trench is easier, because it has real sides. A foundation drain trench 32 feet long, 2 feet wide and 14 inches of empty depth is 64 square feet at 1.1667 feet, which is 74.67 cubic feet, or 2.77 cubic yards.
And for the 24-inch ceiling: a stump hole 4 by 5 feet and 36 inches deep goes in as two runs, 20 square feet at 24 inches for 40 cubic feet, then 20 square feet at 12 inches for another 20. That is 60 cubic feet in total, or 2.22 cubic yards. Both examples here are invented for the page.
Why does the same load weigh more after a week of rain?
Because water has weight and it does not add volume. This site publishes fill dirt at about 2,400 lb per cubic yard dry, which is 1.20 tons, and up to 3,000 lb wet, which is 1.50. The hole still takes the same number of yards either way. What changes is the wheelbarrow.
| What the layer is for on a Maryland lot | Published weight per cubic yard | Tons per yard |
|---|---|---|
| Fill dirt, dry, closing a trench or lifting a low corner | about 2,400 lb | 1.20 |
| The same fill dirt after a spell of storms | up to 3,000 lb | 1.50 |
| Screened topsoil, the four to six inches that go over it | about 2,200 lb | 1.10 |
| Garden soil, blended, filling a raised bed instead | about 2,000 lb | 1.00 |
All four figures are approximate and all four come from this site's own published chart. That the growing materials weigh less than the subsoil is not an accident: what is missing from fill is the organic content, which is exactly why it holds a grade instead of breaking down under one.
Should I leave the 10 percent box ticked for fill that will settle anyway?
Leave it ticked, and then plan the placement as if it were not there. The form adds an allowance of 10 percent for compaction and spillage, and it is worth having on a material you will be wheelbarrowing across grass. What it does not cover is consolidation, which on spread earth runs closer to 10 to 15 percent of the height once rain and traffic have been through.
The way to stop a second order is the way the fill goes in. Place it in 6 to 8 inch layers and compact each one, or at minimum soak each layer and let it settle before the next goes on. For a lawn repair, finish about half an inch proud of the surrounding grade and let the winter bring it level. Nothing woody goes in the hole; buried timber rots out and leaves you filling the same spot in five years.
Timing is the other half of it. Saturated ground smears rather than compacts, and on the flat Coastal Plain ground of the Eastern Shore and Southern Maryland the water table sits close enough to the surface that a low site can stay unworkable for days after a storm. Watch the forecast, keep the pile on high ground and put a tarp over it if weather is coming.
Is this the tool I want, or the topsoil or soil one?
Three calculators cover ground materials on this site and they are not interchangeable.
- This one is for structural fill: grade changes, trench backfill, berm cores, the ground under a base course. Sized on Fill Dirt.
- The topsoil calculator covers the growing layer over the top, usually 4 to 6 inches where grass or planting is going in. That is Top Soil at the lighter figure.
- The soil calculator is the one for blended Garden Soil in raised beds and planting areas.
A regrade is normally two of them run back to back, and the two products arrive as separate lines on the same order.
One Maryland caution before the fill goes down. In the limestone ground of the Hagerstown and Frederick valleys, water drains away through cracks in the rock, and runoff funneled into one place can open a depression. Regrade so the water spreads out across the lawn rather than being aimed at the new low point you have just filled.
What needs to be ready before the truck gets there?
Fill is sold by the cubic yard, so the yardage from the form is the figure that goes in the quantity box on the listing. Choose the date there as well; delivery is arranged at checkout by ZIP code, and the delivery page sets out what the driver needs at the far end. Pick a drop spot on firm, level ground within wheelbarrow distance of the hole, and clear the route before the day rather than on it.
Common questions
How close will the figure be to what I actually need?
The arithmetic is exact; the measuring is not. An averaged depth across an uneven dip is the biggest source of drift, and a hole that looks shallow at the edges is usually deeper in the middle than you guessed. Take the depth at three or four points instead of two if the ground is really irregular, and expect to be within about 10 percent. Rounding the order up to the next half yard covers the rest.
I have the yardage. Where do I go to buy it?
Straight to the Fill Dirt listing, where the quantity and the delivery date are set. If the job also needs a growing layer over the top, run that depth separately and add the topsoil as its own line on the same order so both arrive together.
Where should the pile go if the hole is in the back garden?
Somewhere firm, level and uphill of the work if the ground slopes at all, with clear headroom and enough room for the truck to back in and tip. Earth left on a lawn kills the grass under it within a week or two, so a driveway or a hard standing with a tarp down first is the better choice. Measure the wheelbarrow route for gates and steps before the order goes in.
The result shows tons as well as yards. Which number matters?
Yards is the order. This material is sold by the cubic yard, so that is the figure the listing wants. The tonnage is still worth reading, because it tells you what is actually landing on your drive and how long the spreading will take. A corner needing three yards is around four tons dry, and rather more if it has been sitting in the rain.
Do I measure the empty hole or the finished level?
The empty hole, measured up to where you want the ground to end. Order for that loose volume and build to the compacted one. Earth loses height as it is worked and rained on, which is why the layers go in at 6 to 8 inches and get compacted as they go, and why a lawn repair is left sitting slightly high.
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