How to calculate fill dirt
Fill dirt jobs are almost always about volume: how big is the gap you need to fill? The steps:
- Measure the footprint in feet. For a rectangle, length × width. For a round spot, 3.1416 × (diameter ÷ 2)².
- Find the average depth. Low spots are deepest in the middle. Lay a straight board or a string line across the dip at finished height and measure down to the ground at several points. Average those readings.
- Multiply square feet × depth in feet to get cubic feet. Depth in inches ÷ 12 gives feet.
- Divide by 27 to get cubic yards.
- Add compaction: multiply by 1.15 for 15%, 1.2 for 20%.
Worked example. A 15 × 10 ft dip averaging 8 inches deep:
- 15 × 10 = 150 sq ft
- 150 × (8 ÷ 12) = 100 cubic feet
- 100 ÷ 27 = 3.70 cubic yards measured
- 3.70 × 1.15 = 4.26 cubic yards to order
- At about 1.1 tons per yard, that is 4.69 tons, or one load in a 5-yard single-axle dump truck.
How much does fill dirt compact?
Delivered fill is loose. Packing it down drives out air, and the volume drops. These are rough starting points, not engineering values:
| Fill type | Typical allowance when tamped | Notes |
|---|---|---|
| Sandy fill | about 10–15% | Drains well and settles quickly with water. |
| Common fill dirt (mixed soil) | about 15–20% | The calculator’s default. |
| Clay-heavy fill | about 20–30% | Compacts a lot when worked damp; can crack when it dries. |
| Any fill compacted hard in thin layers | about 20–30% | Plate compactor or roller, lifts of 4–6 in. |
If a building, slab or driveway will sit on the fill, it may need to be engineered structural fill placed and tested to a spec. Ask the builder or engineer what they require before ordering.
Fill dirt per 1,000 square feet
Measured volumes, before the compaction allowance:
| Fill depth | Cubic yards per 1,000 sq ft | Add 15% |
|---|---|---|
| 2 in | 6.2 | 7.1 |
| 4 in | 12.3 | 14.2 |
| 6 in | 18.5 | 21.3 |
| 8 in | 24.7 | 28.4 |
| 12 in | 37.0 | 42.6 |
| 18 in | 55.6 | 63.9 |
| 24 in | 74.1 | 85.2 |
Ordering fill dirt in tons instead of yards
Some yards and quarries sell fill by the ton. Multiply cubic yards by the weight per yard:
| Fill type | About lb per cubic yard | Tons for 10 cubic yards |
|---|---|---|
| Fill dirt, typical | 2,200 | 11 |
| Sandy fill | 2,500 | 12.5 |
| Clay fill | 2,600 | 13 |
| Wet fill | 2,800 | 14 |
Moisture changes the weight more than anything else, so a ton of wet fill gives you fewer yards than a ton of dry. The dirt weight calculator converts both ways.
Tips for placing fill dirt
- Strip the sod and topsoil first in the area you are raising. Burying grass and roots leaves organic matter that rots and settles.
- Fill in layers of 4 to 6 inches, and tamp or roll each layer before adding the next. Slightly damp fill compacts best; soaking-wet fill turns to mud.
- Keep it below the siding. When raising soil next to a house, leave the finished grade several inches below siding and wood framing, and slope it away from the wall. The yard grading calculator covers this.
- Cap with topsoil if you want grass or plants on top. Fill dirt has little organic matter.
- Ask what is in it. Clean fill should be soil without trash, concrete chunks, wood or anything that smells of chemicals. Read what fill dirt is before accepting a free load.
The weights and compaction figures on this page are typical ranges. Your supplier's weight per yard and your soil's behaviour can differ, so confirm the order with them and keep a little margin for the last few inches.
Questions people ask
- How do I estimate fill dirt?
- Measure the length, width and average depth of the area to fill in feet, multiply them to get cubic feet, divide by 27 for cubic yards, then add 15 to 20 percent for compaction. The calculator does all of this and also gives tons and truck loads.
- How much extra fill dirt should I order for compaction?
- About 15 to 20 percent for typical fill that is tamped or watered in. If you compact thin layers with a plate compactor or roller, 20 to 30 percent is safer. Sandy fill shrinks less than clay-heavy fill.
- How many tons is a yard of fill dirt?
- Roughly 1 to 1.4 tons. Dry fill is near 1 ton per yard; damp fill is often around 1.1 to 1.3; wet or clay-heavy fill can be 1.4 tons or more.
- Can I put topsoil straight on fill dirt?
- Yes. A common approach is to bring the area up to a few inches below finished grade with compacted fill, then finish with about 4 to 6 inches of topsoil so grass or plants have something to root into.
- What is the difference between fill dirt and backfill?
- Fill dirt is the material. Backfill is the job of putting dirt back into an excavation such as a trench or around a foundation. You can backfill with the dirt you dug out, with fill dirt you buy, or with sand or gravel when a spec calls for it.