How to Calculate Cut and Fill Volume for a Small Site

A grading bid can swing by thousands of dollars depending on one number: how many cubic yards of dirt have to move. If you need to calculate cut and fill volume for a house pad, a driveway or a small commercial lot, you can get a solid estimate with a survey, a spreadsheet and an afternoon, before any machine shows up.

I do these takeoffs regularly as a civil engineer, and most of the mistakes I see on small sites have nothing to do with complicated math. They come from skipping shrink and swell, ignoring topsoil, or using too few points. This guide walks through the grid method step by step, with a worked example you can copy.

What you need before you start

You need two surfaces: the ground as it exists today and the ground as it should be when grading is done.

• Existing grades. These come from a topographic survey or spot elevations you shoot yourself with a laser level. If you have not worked with one before, our guide on how to read a topographic survey explains contours and spot grades.
• Proposed grades. These come from the grading plan, or for a simple pad, from the finished floor elevation minus the slab and base thickness.
• A grid. On a small site, a 10 foot or 20 foot grid works well. Tighter grids give better accuracy on uneven ground.

How to calculate cut and fill volume with the grid method

The grid method breaks the site into equal squares, works out the average depth of cut or fill in each one, and multiplies by area. It is the same logic that earthwork software uses, just done by hand.

Step 1: Lay out the grid and record elevations

Draw your grid over the site plan. At every corner, write the existing elevation and the proposed elevation.

Step 2: Find the cut or fill depth at each corner

Subtract proposed from existing at each point. A positive number is cut (ground is too high). A negative number is fill (ground is too low). If the existing grade is 102.40 and the proposed is 101.80, that corner is 0.60 feet of cut.

Step 3: Average each square

For each grid square, add the four corner depths and divide by four. That is your average depth for that square.

Step 4: Multiply by area

Multiply each square's average depth by its area. A 20 by 20 foot square is 400 square feet. A square with an average cut of 0.75 feet holds 300 cubic feet of cut.

Step 5: Convert to cubic yards

Divide cubic feet by 27. Contractors price earthwork in cubic yards, and trucks are loaded by the yard. That 300 cubic feet becomes about 11.1 cubic yards.

When a square has some corners in cut and some in fill, the simple average undercounts both. On a small site, the easiest fix is to split those squares into smaller ones, or to calculate cut and fill separately using only the positive or only the negative corners.

A worked example on a house pad

Here is a simplified version of a real 60 by 80 foot pad, broken into 12 squares on a 20 foot grid:

On paper, that is 74.1 cubic yards of cut and 56.3 cubic yards of fill. It looks like the site has a surplus of about 18 yards. That is where most quick estimates stop, and where they go wrong.

Adjusting for shrink, swell and topsoil

Dirt does not occupy the same space in the ground, in the truck and in the compacted fill.

Strip topsoil first

Topsoil is not structural fill. If the site has 6 inches of topsoil over the pad area of 4,800 square feet, that is 2,400 cubic feet, or about 89 cubic yards, that has to come off and be stockpiled or hauled away. It also lowers your existing grade by 0.5 feet across the whole pad, which changes every cut and fill depth. Run the grid again from the stripped surface.

Apply shrinkage to fill

When cut material is placed and compacted, it usually takes up less volume than it did in its natural state. For many silty and clay soils, a shrink factor of 10 to 20 percent is typical. Sandy soils often fall around 5 to 15 percent. So if your fill needs 56.3 compacted cubic yards and your soil shrinks 15 percent, you need about 66 yards of cut to make it.

Apply swell to hauling

Excavated material fluffs up in the truck. Common soils swell 20 to 30 percent, rock even more. If you have 10 yards of surplus in the ground, plan on 12 to 13 loose yards in the truck.

In our example, the 74.1 yards of cut barely covers the 66 yards of fill after shrinkage, leaving roughly 8 yards of surplus, not 18. After stripping topsoil, the pad may actually need imported fill.

Why aiming for a perfect balance can hurt you

A lot of owners hear that the ideal site "balances," meaning cut equals fill and nothing gets trucked in or out. It is a good goal for a large subdivision. On a small residential lot, I often advise against chasing it.

The reason is that not all cut makes good fill. Wet clay, organic layers and material full of roots cannot go under a slab without causing settlement later. Forcing a perfect balance can mean reusing soil that should have been hauled off. Lowering a pad 4 inches to "balance" can also leave it below the surrounding grade, which sends water toward the foundation.

It is usually cheaper to haul 20 yards of poor material and bring in 20 yards of good select fill than to fix a cracked slab five years later. Get the drainage and the soil quality right first, then see how close you are to balance. This is one of the main points in our guide on cut and fill for a first time builder.

Checking your numbers in the field

Once grading starts, compare your estimate to what the crew sees. The surveyor's layout marks show the cut or fill depth at key points, and a quick laser level shot every 20 feet tells you whether the ground is behaving like your grid said it would. If the field shots regularly show deeper cuts than your takeoff, recheck your existing elevations before the next load leaves the site. Remember that rough grade and finish grade are separate passes, as covered in why rough grading and finish grading are not the same job, so leave a few tenths for the finish crew.

Frequently asked questions

How do you calculate cubic yards of fill dirt?

Multiply length by width by average depth in feet to get cubic feet, then divide by 27. Add a shrinkage allowance of 10 to 20 percent for most soils, since compacted fill takes up less space than loose material. For a 20 by 30 foot area filled 1 foot deep, that is about 22 yards before shrinkage.

What is a typical shrink factor for compacted fill?

Many silty and clay soils shrink about 10 to 20 percent when moved and compacted, and sandy soils often shrink 5 to 15 percent. A geotechnical report gives the best number for your site. When no report exists, 15 percent is a common starting assumption on small jobs.

Is the grid method accurate enough for a small site?

For pads, driveways and small lots, a 10 to 20 foot grid usually lands within 5 to 10 percent of a software takeoff. Accuracy drops on steep or very uneven ground. In those cases, tighten the grid or add extra points at breaks in slope.