groundmath

Fill dirt calculator

Measure each area in feet, enter how deep the fill needs to be, and get the yards of dirt to order — with the compacted-fill allowance shown as its own line, per soil type, never silently baked in.

✓ Formula v1.0 · Data v2026.6 · 2 sources · verified 2026-08-02
Areas to fill — measured in feet
Depth of fill
inches
Application and soil — the allowance table is cited below the calculator
You should order

Enter at least one area and a fill depth to see how many yards of dirt to order.

How this is calculated

  1. Shape areas are summed and multiplied by the fill depth:volume = total area × depth (at depth d inches,cubic yards = square feet × d ÷ 324).
  2. For a compacted fill, the dirt to order isfinished volume × (1 + allowance), where the allowance is WisDOT's “expand the fill” range for your soil type — shown as its own line. A loose dump skips it and will settle instead.
  3. No tonnage line, on purpose: engineering sources publish weight-volume conversion factors for aggregates, not natural soil. Fill dirt is bought by the cubic yard; where a supplier quotes by the ton, their scale-ticket conversion governs.

Data used, with sources

ValueUsed asSource
Compaction allowance +10–35 % by soil typeper-soil ranges: clean sands 10–15 %; silty sands 15–25 %; silts 20–30 %; silty clays and clays 25–35 % — default is the full span when the soil type is unknownWisconsin Department of Transportation / Wisconsin Highway Research Program

WisDOT’s "expand the fill" guideline (Table 1.1, WisDOT 2017): a compacted fill consumes 10–35 % more soil than its finished volume, depending on soil type — clean sands the least, silty clays and clays the most. The default 0.20 sits in the overlap of the silty-sand and silt ranges, the middle of the table when the soil type is unknown. WHRP’s Wisconsin field measurements ran lower than the guideline for some soils (clays measured −5 to +9 %), so treat the allowance as a planning margin, not a precision figure.

How many yards of dirt for a given area

The arithmetic is fixed — square feet × depth in inches ÷ 324— so the real work is measuring honestly. Fill depth is rarely uniform: a settling trench is deeper at one end, a low lawn spot feathers to nothing at its edges. Measure the depth at several points and use a representative average, or split the area into sections at different depths and add them as separate entries above. For a hole or an above-ground grade change, measure to the finished grade you want, not to where the dirt pile will first stand — that difference is exactly what the compaction allowance accounts for.

Why the allowance depends on soil type

Sandy fill packs nearly as tight as it arrives; clay arrives in clods full of voids and loses far more volume under the compactor. That is why the cited table runs from10 % for clean sands up to35 % for clays, and why the calculator asks. If you do not know what the pit will send, the full-range default brackets the order — ask the supplier what class of material they are loading, and use their answer.

Common mistakes

  • Ordering the bare geometric volume for a compacted fill.The fill consumes 10–35 % more than the finished shape; that is the allowance line, not a fudge factor.
  • Dumping deep fill in one lift and expecting it to hold grade. Uncompacted fill settles for seasons. If the surface matters, compact in shallow lifts — and if a structure rides on it, that is engineering, not landscaping.
  • Filling planting areas with fill dirt alone.It is subsoil. Cap with topsoil where anything needs to grow.
  • Treating a quoted “yard of dirt” weight as fact. Moisture alone moves a yard by hundreds of pounds; only the scale ticket is real.

Frequently asked

How many yards of dirt do I need?
Measure the area in square feet, measure the depth of fill in inches, then: cubic yards = square feet × depth ÷ 324. A 200 sq ft low spot filled 6 inches deep is 3.7 cubic yards at finished grade — and if the fill will be compacted, add the soil-type allowance the calculator shows as its own line, because a compacted fill consumes more soil than its finished volume.
How much does a yard of dirt weigh?
There is no honest single number — soil texture and moisture swing it too far, and no engineering source publishes a universal tons-per-yard figure for natural soil (WisDOT publishes such conversions for aggregates only). For scale: the dry soil bulk-density range Penn State Extension publishes by texture (1.1–1.6 g/cm³) works out to roughly 1,850–2,700 lb per cubic yard oven-dry, and delivered fill is field-moist and heavier. If you are paying by weight, the supplier's scale ticket governs.
What is the difference between fill dirt and topsoil?
Fill dirt is subsoil — the mineral material below the organic layer — sold to add volume and establish grade. Topsoil is the organic-rich upper layer plants grow in. Use fill dirt for the bulk of a deep fill and cap it with topsoil where anything needs to grow; filling a planting area entirely with fill dirt, or building grade entirely out of expensive topsoil, are both ways to pay for the wrong material.
Why does compacted fill need extra dirt?
Because compaction squeezes the soil into less volume than it occupied in the ground or on the truck. WisDOT's earthwork guideline expands a planned fill by 10–35 % depending on soil type — clean sands the least, clays the most — to estimate how much soil the fill actually consumes. Field measurements in the same report ran lower for some Wisconsin soils, so treat the allowance as a planning margin rather than a precise surcharge.

Sources

Quantities on this page are planning estimates, not engineering advice or a purchase guarantee — product sizes vary by producer, so confirm coverage with your supplier before ordering.Structural fill under buildings, slabs, or pavements is an engineering matter — follow your geotechnical specification and local code.