How to Calculate Excavation, Backfill, and Dirt Truckloads

In the construction industry, dirt is money. Whether you are bidding a foundation excavation, a utility trench, or a grading package, your ability to calculate cubic yards of dirt accurately determines whether you profit or eat the cost of extra trucks and material. Overestimate, and you tie up capital and lose the bid. Underestimate, and you face change orders, angry clients, and profit erosion.

Excavation and backfill are commonly calculated in cubic yards, with 27 cubic feet equal to one cubic yard. That is the foundational number every contractor must memorize. But raw volume is only the starting point. The moment you dig, the soil changes state. It fluffs up (swell), and when you put it back, it compacts down. If you ignore these factors, your truck counts will be wrong every time.

This guide is built for working contractors who need field-ready methods, not classroom theory. We will cover how to measure, how to convert, how to adjust for swell and compaction, and how to translate all of it into truckloads. By the end, you will be able to generate a defensible quantity takeoff for any dirt-related scope and source material or disposal sites through marketplaces like NeedsDirt.com.

The best bid is not the lowest number. It is the most accurate number. Dirt quantities drive trucking costs, and trucking is often 40 to 60 percent of an excavation bid.

Before you touch a calculator, you need to understand the three volumes every project has: bank volume (in-place soil), loose volume (after excavation), and compacted volume (after placement and compaction). Each serves a different purpose in your estimate. Bank volume is what you bid for excavation. Loose volume is what you haul. Compacted volume is what you need to fill a hole to a specified density.

Getting from one to the other requires basic arithmetic and a few standard multipliers. The sections that follow walk you through each step with real numbers, so you can apply them directly to your next takeoff.

The primary keyword here is simple: how to calculate cubic yards of dirt. The formula is always the same, no matter the shape. Measure length, width, and depth in feet, multiply them together to get cubic feet, then divide by 27 to get cubic yards.

Formula: (Length x Width x Depth) / 27 = Cubic Yards

For rectangular excavations, this is straightforward. For example, a foundation trench 40 ft long, 3 ft wide, and 4 ft deep yields 40 x 3 x 4 = 480 cubic feet. Divide by 27 and you get 17.78 cubic yards. Round up to 18 cubic yards for bidding.

For circular or cylindrical shapes, such as pier holes or round tanks, use the formula for volume of a cylinder: Pi x radius squared x depth. Pi is 3.14. If you have a hole 2 ft in diameter (1 ft radius) and 4 ft deep, the math is 3.14 x 1 x 1 x 4 = 12.56 cubic feet, or 0.47 cubic yards.

For irregular shapes, break the area into smaller regular shapes, calculate each, and sum them. This is common with trenches that change depth or width. You can also use the average end area method for long trenches where cross-sections vary: average the square footage of the two ends and multiply by the length.

Field shortcut: If you measure in inches for depth, convert to feet by dividing by 12. A 6 in. depth is 0.5 ft. An 8 in. depth is 0.67 ft. A 4 in. depth is 0.33 ft.

For an excavation calculator, you can build a simple spreadsheet or use a mobile app, but the math above is all you need. The key is consistency in units. Never mix feet and inches without converting.

When you calculate how many truckloads of dirt do I need, you must first know the volume in cubic yards. That is the number you will adjust for swell and compaction. Without a solid cubic yard takeoff, every downstream calculation is garbage.

Always add a waste factor. For excavation, 5 to 10 percent is typical for over-excavation, spillage, and uneven subgrade. For backfill, 10 to 15 percent is common because compaction never achieves 100 percent of the theoretical volume. These factors are not optional; they are the difference between a complete bid and a callback.

Soil does not stay the same volume when you move it. This is the single biggest mistake in dirt takeoffs. Bank soil, when excavated, swells because it loses density and gains air voids. The swell factor is a percentage increase over the bank volume. Typical swell factors are 15 to 25 percent for common earth, 25 to 35 percent for clay, and 10 to 15 percent for sand and gravel.

Loose volume = Bank volume x (1 + Swell factor)

If you excavate 100 cubic yards of clay with a 30 percent swell, you will haul 130 cubic yards of loose material. That means more truckloads than the hole suggests. If you bid 100 cubic yards of hauling, you will lose money on every load.

Compaction works in the opposite direction. When you place backfill and compact it, the volume shrinks. The shrinkage factor is the percentage decrease from loose volume to compacted volume. Typical shrinkage is 10 to 20 percent. To determine how much bank soil you need to yield a required compacted fill, use this formula:

Bank volume required = Compacted volume / (1 - Shrinkage factor)

If you need 100 cubic yards of compacted fill and the shrinkage is 15 percent, you need 100 / 0.85 = 117.6 cubic yards of bank soil. That means you must excavate or import 118 cubic yards to fill the hole to grade.

For imported fill, you order loose cubic yards from the supplier, but you pay for what you place and compact. Always clarify with the supplier whether they sell by bank cubic yard or loose cubic yard. The difference can be 20 to 30 percent.

When you are calculating how many truckloads of dirt do I need, you must decide which volume you are hauling. If you are hauling excavated spoils off-site, use loose volume. If you are importing fill, use the loose volume the truck delivers. If you are backfilling with on-site material, you need to know both the loose volume you stockpile and the compacted volume you place.

A simple field test for shrink and swell is to fill a 5-gallon bucket with bank soil, compact it, and measure the volume change. It is not lab-accurate, but it will give you a feel for the soil on your site. For large projects, a geotechnical report will provide specific values.

Never assume a 1:1 ratio between dug and hauled. The swell factor alone can add 20 percent to your truck count. Add compaction and waste, and you are looking at a 40 percent difference between the hole and the loads.

If you need to find fill dirt or dispose of spoils, NeedsDirt.com connects you with local sources and dump sites that understand these volume differences. You can specify bank or loose yards and avoid surprises.

Once you know your loose cubic yards, converting to truckloads is a matter of dividing by the capacity of your truck. But truck capacity is not one-size-fits-all. A standard tandem-axle dump truck carries 10 to 14 cubic yards. A tri-axle carries 15 to 18 cubic yards. A quad-axle carries 20 to 22 cubic yards. A semi-end dump can carry 25 to 30 cubic yards, and a belly dump or side dump can carry similar volumes depending on length.

However, legal weight limits often cap the load before volume does. A tandem axle is typically limited to 13 tons (26,000 lbs) of payload. If the soil weighs 1.3 tons per cubic yard, that is 10 cubic yards. If it weighs 1.1 tons per cubic yard, that is 11.8 cubic yards. You must know the density of your material. Typical densities are:

• Topsoil: 1.1 to 1.3 tons per cubic yard
• Common earth: 1.2 to 1.4 tons per cubic yard
• Clay: 1.3 to 1.5 tons per cubic yard
• Sand and gravel: 1.4 to 1.7 tons per cubic yard
• Crushed stone: 1.35 to 1.5 tons per cubic yard

To calculate how many truckloads of dirt do I need, use the lower of the two limits: volume capacity or weight capacity. For a tandem axle with a 14 cubic yard bed and a 13-ton legal payload, hauling clay at 1.4 tons per cubic yard, the weight limit allows 13 / 1.4 = 9.3 cubic yards. So you can only load 9 cubic yards per trip, not 14.

Number of truckloads = Total loose cubic yards / Cubic yards per load

If you have 500 loose cubic yards and each truck carries 9 cubic yards, you need 56 loads. Add one load for spillage and rounding. That is 57 loads. At $120 per hour for a truck and driver, and a 30-minute round trip, that is 28.5 hours, or roughly $3,420 in trucking alone. If you bid 40 loads, you just lost $2,000.

For import, the same math applies, but you also pay for the material. If you need 200 compacted cubic yards and the shrinkage is 15 percent, you need 235 bank cubic yards. The supplier sells loose cubic yards, and the swell is 20 percent, so you need 235 x 1.2 = 282 loose cubic yards. At 9 cubic yards per load, that is 32 loads.

Always ask the supplier or dump site for their truck capacity and weight limits. NeedsDirt.com lists material sources and dump sites with details that help you plan hauling. You can also find contractors with their own trucks to reduce costs.

Let us walk through a complete example. You are excavating a rectangular basement 30 ft by 40 ft, 8 ft deep, in common earth with a swell factor of 20 percent and a shrinkage factor of 15 percent. You will haul off the spoils and import clean fill for backfill. The truck is a tri-axle with a 16 cubic yard bed and a 20-ton payload limit. The soil density is 1.3 tons per cubic yard.

Step 1: Calculate bank volume. 30 x 40 x 8 = 9,600 cubic feet. Divide by 27 = 355.6 cubic yards. Add 5 percent waste for over-excavation = 373.4 cubic yards. Round to 374 bank cubic yards.

Step 2: Calculate loose volume for hauling. 374 x 1.20 = 448.8 loose cubic yards.

Step 3: Determine truck capacity. Volume limit: 16 cubic yards. Weight limit: 20 tons / 1.3 tons per cubic yard = 15.4 cubic yards. The weight limit governs, so use 15 cubic yards per load.

Step 4: Calculate haul loads. 448.8 / 15 = 29.9 loads. Round up to 30 loads.

Step 5: Calculate backfill volume. Assume you need to backfill 100 compacted cubic yards against the foundation. Bank volume required = 100 / (1 - 0.15) = 117.6 bank cubic yards. Since you are importing, you need loose volume: 117.6 x 1.20 = 141.1 loose cubic yards. At 15 cubic yards per load, that is 9.4 loads, round to 10 loads.

Step 6: Calculate total truckloads. 30 loads out + 10 loads in = 40 loads. At $120 per hour and a 45-minute round trip, each load takes 0.75 hours. 40 x 0.75 = 30 hours. Trucking cost = 30 x $120 = $3,600.

This is the level of detail that separates a winning bid from a losing one. Notice how the waste factor, swell, and shrinkage each added loads. If you had used the raw 355.6 cubic yards and a 16 cubic yard truck, you would have calculated 23 loads. You would have been 7 loads short on hauling and 10 loads short on import. That is a 17-load error, or over $1,500 in trucking alone.

Use this same framework for any excavation calculator. Measure the hole, convert to bank cubic yards, apply swell for hauling, apply shrinkage for backfill, and divide by the effective truck capacity. Always verify weight limits with your trucking provider.

Not all excavated material is suitable for backfill. Organic topsoil, expansive clays, and contaminated soils must be hauled off. In those cases, you import clean fill. The decision affects both quantity and cost.

If you can reuse on-site material, you avoid import costs but you still pay for handling and compaction. You also need to stockpile the material separately. The volume you stockpile is loose cubic yards. To place 100 compacted cubic yards, you need 117.6 bank cubic yards, which is 141.1 loose cubic yards. If your stockpile is 141 loose cubic yards, you have enough. If it is only 100 loose cubic yards, you are 41 cubic yards short and must import.

Import fill costs vary by region and material. Common fill dirt ranges from $10 to $30 per cubic yard delivered, plus trucking. Screened topsoil can be $25 to $50 per cubic yard. Crushed stone base can be $30 to $60 per cubic yard. If you need to dispose of spoils, dump fees range from $20 to $80 per load, depending on the site and material.

NeedsDirt.com is a marketplace where contractors find fill dirt, dump sites, and excavation material. You can browse listings for free fill dirt, sometimes just paying for trucking, or find dump sites that accept clean fill at lower rates. This can turn a disposal cost into a savings if you match your spoils with a site that needs fill.

When you calculate how many truckloads of dirt do I need, factor in the cost of both import and disposal. If you can balance the site, you reduce both. A balanced site is one where the cut equals the fill, adjusted for swell and shrinkage. In practice, perfect balance is rare, but you can get close.

For a balanced site, you need to calculate the net volume. If you excavate 500 bank cubic yards and need 400 compacted cubic yards of fill, the bank volume required for fill is 400 / 0.85 = 470.5 bank cubic yards. You have 500 - 470.5 = 29.5 bank cubic yards of excess. That excess becomes loose at 20 percent swell = 35.4 loose cubic yards, or about 3 truckloads to haul off. If you had ignored shrink, you would have thought you had 100 cubic yards excess, or 8 loads. The difference is 5 loads, or $600 in trucking.

Always run the numbers both ways and price the job with the accurate net volume. Then source material or disposal through NeedsDirt.com to lock in rates before you bid.

Even with the formulas, field conditions can throw off your calculations. Here are practical tips to keep your takeoff honest.

• Measure twice, dig once. Use a laser level or transit for depth. A tape measure and string line can sag or slope. A 6 in. error over 40 ft is 20 cubic feet, or 0.74 cubic yards, per trench section.
• Account for subgrade compaction. If the geotech requires 95 percent compaction, you need more fill than a 90 percent requirement. The shrinkage factor increases. Ask for the Proctor curve.
• Do not forget the topsoil strip. If you strip 6 in. of topsoil over a 5,000 sq ft area, that is 2,500 cubic feet, or 92.6 cubic yards of bank volume. That is 111 loose cubic yards, or 7 to 11 truckloads depending on truck size. Many bids miss this.
• Check for rock. Rock does not swell like soil. It can be sold as riprap or crushed. If you hit rock, your excavation cost per cubic yard can triple. Have a contingency.
• Use a spreadsheet. Build a simple excavation calculator with columns for length, width, depth, cubic feet, cubic yards, swell, shrink, waste, and truckloads. Save it for every job.
• Verify truck capacity in writing. Do not assume a tri-axle carries 18 cubic yards. Ask for the bed volume and the legal payload. Get it in the contract.
• Track loads on site. Use a load ticket system. Count every truck. A 5 percent error in load count on a 100-load job is 5 loads, or $600.

Common mistakes include using compacted volume for hauling, ignoring swell, forgetting waste, and mixing units. Another is using the wrong density for weight limits. If you haul dry sand at 1.1 tons per cubic yard, a 20-ton truck can carry 18.2 cubic yards, but the bed may only hold 16. You must use the lower limit.

Finally, document your assumptions. If the client or general contractor questions your quantity, you can show the math. A transparent takeoff builds trust and reduces change order disputes.

When you need to find fill dirt or a dump site, NeedsDirt.com lets you search by location and material type. You can compare prices and trucking distances, which directly affects your load count and cost. The marketplace is built for contractors who need reliable, local solutions.

Master these calculations and you will bid with confidence. Dirt is a commodity, but the math behind it is your competitive advantage.