How to use the dirt calculator
- Measure the area to fill. For a hole or trench, use its length and width; for a low spot in a yard, outline it and estimate the shape.
- Find the average depth. Run a string line at the finished grade and measure down at several points. Average them.
- Keep the compaction allowance (20%) if the fill will be compacted or driven on. Loose dirt settles as air is squeezed out.
- Choose the soil type. Wet clay is far heavier than dry loose dirt, which matters if you are hauling it yourself.
The fill dirt formula
Cubic yards = area (sq ft) × depth (in) ÷ 12 × (1 + compaction %) × (1 + waste %) ÷ 27
Tons = cubic yards × 27 × density (lb/ft³) ÷ 2,000
Densities from The Engineering ToolBox: loose dry dirt 1,220 kg/m³ (76 lb/ft³), moist excavated earth 1,442 kg/m³ (90 lb/ft³), moist packed dirt about 1,600 kg/m³ (100 lb/ft³), and wet excavated clay 1,826 kg/m³ (114 lb/ft³). Delivered fill is usually somewhat moist, so the default is 90 lb/ft³, about 1.2 tons per cubic yard.
Why compaction matters
Soil delivered loose from a truck contains a lot of air. When it is compacted with a plate compactor, roller or simply rain and foot traffic, its volume shrinks — typically 10–25% for common soils. If you order exactly the finished volume, you will come up short. Use about 10% for fill that will only settle naturally under lawn, and 20–25% for fill that will be mechanically compacted under a slab, patio or driveway.
Worked example: filling a low area
A low spot in a yard is about 20 × 15 ft and needs an average of 6 inches of fill, compacted, with 5% waste:
- Area: 20 × 15 = 300 sq ft
- Finished volume: 300 × 6 ÷ 12 = 150 cu ft
- To order: 150 × 1.20 × 1.05 = 189 cu ft = 7.0 yd³
- Weight at 90 lb/ft³: 17,010 lb = 8.5 tons
That is about one tandem-axle dump truck load. A half-ton pickup can usually carry only about a third to half of a cubic yard of moist dirt safely, so check your payload rating before hauling it yourself.
Fill dirt vs. topsoil
- Fill dirt is subsoil with little organic matter. It is stable, compacts well and is cheap — ideal for raising grade, backfilling foundations and filling holes.
- Topsoil is the dark, organic top layer that plants grow in. It is more expensive and settles more. Use it only for the top 4–6 inches where grass or plants will grow; see the topsoil calculator.
A typical lawn regrade uses fill dirt for the bulk of the depth, capped with topsoil.
Tips
- Grade away from the house. A common guideline (IRC R401.3) is to slope soil at least 6 inches of fall over the first 10 ft away from a foundation.
- Compact in lifts of 4–6 inches, lightly moist, rather than all at once.
- Ask what is in it. "Clean fill" should be free of debris, roots and large rocks.
- Call 811 before digging or regrading near buried utilities.
Frequently asked questions
How much does a yard of fill dirt weigh?
Typically about 1.0 to 1.4 tons per cubic yard depending on moisture and soil type; about 1.2 tons is a good planning figure for moist fill.
How much fill dirt do I need?
Multiply area by depth in feet and divide by 27 for cubic yards, then add about 20% if the fill will be compacted.
How many cubic yards of dirt are in a dump truck?
A small single-axle dump truck carries roughly 5–7 cubic yards of dirt; a tandem-axle truck typically carries about 10–12 cubic yards, limited by weight.
How much does dirt compact?
Loose soil typically shrinks 10–25% when compacted. Order 10% extra for natural settling and about 20–25% for mechanically compacted fill.
Is fill dirt or topsoil better for filling holes?
Fill dirt is better for the bulk of the hole because it compacts and does not decompose. Finish with a few inches of topsoil if grass will grow there.