Dirt Calculator for a Low Corner, a Trench and the Gap Between Them
Enter your project dimensions
Two days after an August downpour you can still see exactly which part of the yard needs fill, because that is the part with water standing on it. Walk the wet outline while it is visible and drive a stake at the deepest point. Everything this dirt calculator does starts from those two measurements, and the size of what you order depends far more on which shape you are filling than on how bad the puddle looked.
A ponding back corner against a trench beside the fence
Take two jobs off the same property, both hypothetical and both with round numbers.
The back corner holds water and measures roughly 30 by 22 feet, deepest at five and a half inches and shallow to nothing at the edges, so the average raise is about three inches. That is 660 square feet. 660 x 3 = 1,980, divided by 12 is 165 cubic feet, divided by 27 is 6.11 cubic yards. Fill dirt is published here at about 2,400 lb a cubic yard when dry, or 1.20 tons, so that is 7.3 tons. With the 10 percent box ticked, 6.72 cubic yards and 8.0 tons.
The trench along the fence, backfilled after a water line went in, runs 25 feet at 18 inches wide and 18 inches deep. In the tool that is 25 by 1.5 feet, which is 37.5 square feet, at a depth of 18 inches. 37.5 x 18 = 675, divided by 12 is 56.25 cubic feet, divided by 27 is 2.08 cubic yards, or 2.5 tons. With the allowance, 2.29 yards and 2.75 tons.
Both look like small jobs standing in the yard. One is three times the other.
What the dirt calculator asks once you have an average depth
Choose Rectangle for a trench, a berm or a squared-off patch. Choose Circle and give one diameter for a round depression or an old stump hole. Choose Multiple areas and add up to five pieces when the low ground wanders across the lot. Lengths, widths and diameters go in as feet. Depth goes in as inches, anywhere from a quarter inch to 24, which is why a deep hole is entered as a depth in inches rather than a depth in feet.
Under the depth field is the material select, which sets the weight used for the tons line, and a checkbox, ticked by default, that adds 10 percent for compaction and spillage and can be unticked. Press calculate and the results box gives cubic yards, tons and cubic feet at once, with a button to email the figure to yourself.
For an uneven hollow, the field that needs care is depth. Measure at the deepest point, measure at the shallow edge, and enter the average of the two. Guessing from the middle of a saucer-shaped depression usually overstates it.
From cubic feet to yards, and why a wet yard rides heavier
Cubic feet is the volume you just described: area in square feet times depth in inches, divided by 12. Divide by 27 for cubic yards, since a yard is a three-foot cube, and that is the unit fill is loaded and delivered in. The tons line converts that volume using the published weight of the material.
Rain changes weight without changing volume. Dry fill dirt is about 2,400 lb a yard here. Soaked through after a week of afternoon storms, that same yard can approach 3,000 lb, which is the figure the site publishes for wet fill. The order does not change, but the wheelbarrow does, and so does whether the material spreads or smears. Fill that arrives saturated will not compact, so a delivery booked into a dry stretch is worth more than an extra yard.
Leaving the surface proud where sand settles under the first storm
Fill placed in one deep dump keeps settling for months. Place it in lifts of six to eight inches, compact or at least soak and consolidate each one, and on a lawn repair finish about half an inch high so the first heavy rain brings it flush rather than dished.
The 10 percent checkbox covers spillage and the material that disappears into the wheelbarrow route. It does not cover settlement over a deep fill, so on anything over a foot deep, order to the top of your range rather than the bottom. Keep organic debris out of the fill entirely. Buried wood rots and leaves a soft pocket years later, which is the last thing you want on ground where limestone already lies under the sand in parts of the state.
Anything structural under a slab or a footing is a different conversation, with thinner lifts and a compaction specification from an engineer. This tool sizes the material, not the specification.
Fill dirt, topsoil or garden soil: three tools, three weights
The mix-up here costs people a whole delivery, so plainly:
Use this dirt calculator and Fill Dirt for the structural layer. Screened mineral subsoil, low in organic matter, about 2,400 lb a cubic yard. It is what goes in a trench, under a pad, into a hollow and inside a berm. Nothing grows well in it, and that is the point.
Use the topsoil calculator and Top Soil for the growing layer that goes on afterwards, four to six inches of it, and only where grass or planting is going. Screened topsoil is published at about 2,200 lb a yard, or 1.10 tons.
Use the soil calculator and Garden Soil for raised beds and planting holes, where a blended mix is wanted rather than native sand. That one is the lightest of the three at around 2,000 lb a yard, an even 1.00 ton.
Bring the fill up to within four to six inches of your finished grade, then switch tools and order the growing layer as a second line. Two numbers, two products, one delivery. If you are unsure which layer you are actually short of, send the measurements and a photo of the low spot through the contact page before you order.
Common questions
The low ground slopes away toward the fence. How do I measure a depth on that?
Run a string line level from the high side to a stake at the low side and measure down to the ground at three or four points along it. Average those readings and enter that as the depth. On a slope the shallow end is often nearly zero, so an average taken from only the deep end can double your order.
The wet patch is a long curve, not a rectangle. What should I enter?
Box it. Enter the smallest rectangle that covers the curve, or split it under Multiple areas into two or three rectangles that follow its shape. Fill is cheap to have a little of left over and awkward to be short of halfway through a wheelbarrow run.
Should I include the bed border or the edging around the area I am filling?
Only if the fill goes under it. Measure to the inside face where a raised border already sits on firm ground, and to the outside of the line where you are building the grade up first and setting the border afterwards.
I need fill and I need something to grow grass in. How do I order both?
Calculate the fill to within four to six inches of your finished level and order Fill Dirt for that. Then run the topsoil calculator on the same footprint at four to six inches and order Top Soil as a separate line. Keep the two piles apart on delivery day so the growing layer does not get mixed into the structural one.
How do I fill an old stump hole with sloping sides?
Use Circle mode with the diameter measured across the top, then enter roughly two thirds of the deepest reading as the depth, since the sides taper in. Fill it in layers, soaking each one, and expect to come back once after the rains to top it off.
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