Fill Dirt Calculator

How to calculate how much fill dirt you need

Fill dirt is sold by the cubic yard or by the ton, and you work out both from the length and width of the area in feet and the depth you need to raise it, in inches.

Cubic yards = length (ft) × width (ft) × depth (in) ÷ 324
Tons = cubic yards × about 1.1
Order = cubic yards × 1.15 to 1.25 for a compacted fill

When the depth is in feet, as it is for holes, pools and trenches, multiply length × width × depth in feet and divide by 27 instead. The calculator above takes depth in inches (or centimetres in metric), so enter 3 ft as 36 in. It shows cubic yards, cubic feet, cubic metres, tons and tonnes.

1. Measure the area. Split irregular areas into rectangles, circles and triangles and add them.
2. Find the average depth. For a sloping fill, take depth readings at several points along a string line and average them.
3. Add for compaction. Loose fill takes up less room once it is compacted; the compaction section below explains the 15–25% range. Digging works the other way: soil swells when it comes out of the ground, so to haul dirt away use the excavation calculator for loose yards and truckloads.
4. Convert to tons if the supplier sells by weight, using their weight per yard when they give one.

Fill dirt for common areas and depths

Most fill jobs are a known area raised by a set depth. The table gives the compacted volume and weight for common sizes at 3, 6, 12 and 24 in, using the calculator’s fill dirt preset of 1.1 tons per cubic yard. Add your compaction allowance to the yards before you order.

Fill volumes climb quickly. Raising a 30 × 40 ft area by just 12 in is 44.44 yd³ before compaction, which is several truckloads. Ask the supplier how many cubic yards each of their trucks carries and divide.

How much extra fill dirt to order for compaction

Fill takes up less space once it is placed and compacted, and some is lost in hauling and settlement, so the volume you order has to be larger than the space you are filling. The Indiana Department of Transportation’s design manual states that fill quantities must be adjusted by a shrinkage factor to account for compaction, hauling losses, settlement of the ground underneath, erosion and clearing. For divided and two-lane roadway projects it recommends preliminary factors of 15% to 25%, with the higher figure for smaller quantities, and 30% to 35% for shoulder-widening projects. It notes that sand and gravel shrink less than clay or silt.

These are highway figures, not a residential rule, so ask your supplier or engineer for an allowance that suits your material. The calculator’s extra setting goes up to 20%; for a larger allowance, set it to None and multiply the cubic yards yourself (for example by 1.25 for 25%).

Use 10% only for a thin, loosely placed fill that will not be compacted, such as filling a shallow dip under grass. Use 20–25% for anything that will be compacted with a plate or roller, or that has to carry a slab, shed or driveway. Structural fill under a building or driveway should follow your plans or a geotechnical engineer’s specification; this calculator gives the quantity, not the compaction requirement.

How much does a yard of fill dirt weigh?

The calculator uses 1.1 tons (2,200 lb) per cubic yard for fill dirt as a typical planning figure; use your supplier’s weight per yard when they give one. For comparison, the USDA Natural Resources Conservation Service’s soil-quality sheet on bulk density says that, since most rock has a density of about 2.65 g/cm³, a medium-textured soil with about 50% pore space has an ideal bulk density of 1.33 g/cm³. Converted, 1.33 g/cm³ is about 2,242 lb, or 1.12 tons, per cubic yard of dry, in-place soil. The same sheet notes that loose, porous soils have lower bulk density, so loose fill on a truck can weigh less.

Real fill varies around that figure for three reasons:

• Water. Bulk density is measured on dry soil. Wet fill carries the weight of its water as well, so a truckload after rain weighs more than the same volume in summer.
• Texture. NRCS notes that sandy soils have relatively high bulk density because sand has less total pore space than silt or clay.
• Compaction. Fill that has been compacted packs more soil into each cubic yard. That is the same effect the shrinkage factor accounts for.

If you need to move between tons and yards for a quote, the tons to cubic yards converter has a fill dirt preset.

Filling holes, ponds, pools and trenches

For anything deeper than it is wide, measure in feet and use the box or cylinder formula rather than the inches formula.

• Box or rectangle: length × width × depth (ft) ÷ 27 = cubic yards.
• Round hole or pond: 3.1416 × radius² × depth (ft) ÷ 27, where the radius is half the diameter.
• Sloped sides: measure the width halfway down and use that as the average width.

An in-ground pool is the same calculation at a bigger scale. A 12 × 24 ft pool with an average depth of 4 ft holds 1,152 ft³, or 42.67 yd³, and with 20% for compaction needs about 51.2 yd³, roughly 56 tons. Pool removal usually involves a permit, drainage holes in the shell and a specified backfill, so check with your local building department before you order.

Filling low spots and grading a yard

Grading jobs rarely have one depth. Find the average with a string line: stretch a level string across the area at the finished height and measure down to the ground every few feet. Average those readings and use the result as the depth. Do not just halve the deepest reading: a dip that tapers evenly from a deep centre to zero at every edge averages only about a third of its deepest point.

A 10 × 15 ft dip whose string-line readings average about 4 in needs 150 × 4 ÷ 324 = 1.85 yd³, about 2.04 tons, or about 2.2 tons with 10% extra. Where grass or plants will grow, replace the top few inches of fill with topsoil, because fill is chosen to compact and support weight, not to grow roots. For a dip only an inch or two deep in an existing lawn, a topsoil or sand top-dressing is usually the better choice; see the topsoil calculator.

Around a house, the finished grade generally needs to fall away from the foundation so water drains off. The required slope and the distance it runs are set by your local building code, so check it before you finalize the depth; the calculator then gives the volume for whatever depths the slope produces. Keep fill below siding and weep openings.

Fill dirt in metric

At 1.1 US tons per cubic yard, the fill dirt preset is about 1.31 tonnes per m³. Metric jobs need no 324: multiply length × width × depth in metres.

One cubic metre of fill covers 10 m² at 100 mm, 6.7 m² at 150 mm and 3.3 m² at 300 mm.

What to ask the supplier before ordering fill

“Fill dirt” covers anything from clean, screened subsoil to whatever came out of the last excavation, so a few questions up front save trouble later.

• Is it screened? Screened fill has had rocks, roots and debris removed. Unscreened fill is cheaper but can contain material that rots and settles.
• What is it made of? Sandy fill drains and compacts differently from clay fill. NRCS notes that bulk density depends on soil texture, and the Indiana DOT manual notes that sand and gravel shrink less than clay or silt, so the soil type affects both the weight per yard and the compaction allowance.
• Is it sold by the yard or the ton? If by the ton, ask for their weight per yard and multiply your cubic yards by it. If by the yard, the calculator’s volume plus your compaction allowance is the order.
• How much does each truck carry? Divide your order by the truck capacity and round up, so you know how many loads to expect.
• Where can the truck tip? A loaded truck is heavy. Keep it off septic systems, drain lines, and soft lawn that will rut.

If the fill will support a structure, such as a shed slab, a driveway or a building addition, ask what fill your plans or engineer require. Many projects call for a specific granular material instead of general fill, which you would size on the gravel calculator.

Spreading and compacting fill

The quantity the calculator gives assumes the fill ends up at the finished height after compaction. That only happens if the fill is placed and compacted in layers rather than dumped in one pass. Thick, loose layers bridge over voids and settle unevenly later, which is why a fill that looks level on day one can show a dip after the first wet season.

Plan the work so each layer is spread, leveled and compacted before the next arrives. Light fills over an existing lawn can be raked in and watered to settle, but fills that will carry weight need a plate compactor or roller. Keep heavy equipment away from foundation walls and buried utilities, and call your local utility-locating service before you dig or regrade.

Give a new fill time before you build on it or finish it. Water and seasons settle loose soil further, and it is easier to add a little more fill to a dip in a few weeks than to lift pavers or a shed later. Keep a few spare yards in mind when you plan the budget.

Fill that will be planted should end a few inches below the final grade so there is room for the topsoil layer. Measure that allowance into your depths now: if the finished surface must rise 12 in and you want 4 in of topsoil, the fill depth in the calculator is 8 in.

Common mistakes when ordering fill dirt

• Ordering the hole volume exactly. The hole is a compacted volume, and fill shrinks as it is compacted. Add 15–25% (the Indiana DOT planning range for road earthwork, with the higher figure for smaller jobs), or ask your supplier how much extra they recommend for their material.
• Using fill where things should grow. Fill dirt is subsoil. Cap planting areas with topsoil instead of trying to grow grass in fill.
• Burying debris and organic matter. Stumps, roots, sod and trash decompose and leave voids that settle later. Ask the supplier whether the fill is screened and clean.
• Placing it all at once. Thick, loose layers settle unevenly. Spread fill in layers and compact each one, as your plans or local guidance specify.
• Changing the drainage. Raising one area can send water toward a neighbor’s yard or your own foundation. Check the slope before you order, not after.
• Mixing up tons and yards. At 1.1 tons per yard the two numbers are close but not the same; confirm which unit the quote uses. The calculator’s price field is set to cubic yards.

Fill dirt vs topsoil, sand and gravel calculators: which one to use

All of these use the same volume formula; the material and the job decide which page fits.

• Fill dirt calculator (this page): raising ground, backfilling holes, trenches, ponds and pools, and grading, with a compaction allowance.
• Topsoil calculator: the growing layer on lawns and beds, including top-dressing and the soil cap over fill.
• Raised bed soil calculator: soil mixes for raised garden beds by the bag or yard.
• Gravel calculator: stone bases for slabs, sheds and paths, and drainage stone.
• Sand calculator: sand for paver beds, sandboxes and pool bases.
• Cubic yard calculator: any shape, any material, when you just need the volume.