How Much Fill Dirt Do I Need? Calculator & Guide

Fill dirt is the unsung workhorse of yard projects. Before you can install a new lawn, backfill a foundation, or raise low-lying ground, you need fill dirt to get the grade right. The math is straightforward — but there's one step most homeowners miss that leads to coming up short on delivery day.

This guide covers how to calculate fill dirt accurately (including the compaction factor), how fill dirt is sold, realistic costs, how to find it free, and how it differs from topsoil. For a fast estimate, use the calculator below.

Fill Dirt Calculator

Enter your project area and fill depth below. The result is your raw calculation — remember to add 15% before ordering.

The Formula

Fill dirt is sold by the cubic yard. The base formula is:

Length (ft) × Width (ft) × Depth (in) ÷ 324 = Cubic Yards

The 324 is the shortcut that converts feet and inches to cubic yards in one step (27 cubic feet per yard × 12 inches per foot = 324). One cubic yard of fill dirt weighs approximately 1.5 tons, though this varies by soil type — clay fill is heavier, sandy fill is lighter.

Then add 15% for compaction:

Calculated Cubic Yards × 1.15 = Amount to Order

This is the step that trips people up. More on why below.

The Compaction Factor: Why You Need More Than You Calculate

Loose fill dirt that arrives on a truck has air pockets and voids throughout. When you compact it in layers — as you must — it reduces in volume by 10–15%. A project that calculates to 10 cubic yards will settle to roughly 8.5–9 cubic yards after proper compaction.

This means you need to order 10–15% more than your raw calculation to end up with the right in-place volume. Always apply the 1.15 multiplier before you place your order.

Example: 20×20 ft Yard Low Spot, 6 Inches Deep

20 × 20 × 6 ÷ 324 = 7.41 cubic yards (raw calculation)

7.41 × 1.15 = 8.5 cubic yards to order

At 1.5 tons per cubic yard, that's about 12.75 tons — comfortably within a single tandem-axle dump truck load of 10–12 yards. Round up to 9 yards to account for any irregularities in your area.

How Much Fill Dirt Do I Need? Project-by-Project Guide

Fill depth varies widely depending on what you're doing. Here's a breakdown by common project type:

Fill Dirt for Yard Grading

Grading is the most common residential fill dirt use — correcting low spots, directing water away from structures, or raising a section of yard to match the surrounding grade. The goal is a surface that slopes gently away from your foundation and any structures.

Standard Grading Slope

The standard drainage slope is 6 inches of drop over the first 10 feet away from a foundation, then a gentler 1–2% grade beyond that. If your yard currently slopes toward your house, fill dirt is how you correct it.

How Much Fill for Common Yard Areas

Fill Dirt for Backfilling Around a Foundation

After construction or when correcting drainage issues, backfilling around a foundation is critical for keeping water away from your basement or crawlspace. Poor grading is one of the top causes of residential water intrusion.

For a foundation backfill strip 3 feet wide and 2 feet deep around a typical 30×40 ft house footprint:

Perimeter = 2(30 + 40) = 140 ft
Volume = 140 ft × 3 ft × 24 in. ÷ 324 = 31.1 cubic yards
Order: 31.1 × 1.15 ≈ 35.8 cubic yards (3–4 truckloads)

Use compactable fill (clay-heavy subsoil works well here — it sheds water). Never use sandy fill against a foundation since it drains water directly toward the wall.

Fill Dirt Cost: And How to Get It Free

Fill dirt is uniquely positioned in the landscape materials world: it's often the one material you can get at zero cost for materials.

How to Find Free Fill Dirt

Excavation contractors dig up subsoil constantly — for pools, foundations, utility lines, and road projects. That subsoil has to go somewhere. If you can accept a dump, many contractors will deliver for free or for a nominal fuel charge.

• Craigslist & Facebook Marketplace— Search “free fill dirt” in your area. New listings appear frequently near active construction zones.
• Local excavation companies — Call contractors actively working in your area. Offer your property as a dump site; they save landfill tipping fees, you get free fill.
• Utility projects — Gas, water, and telecom line installations generate large amounts of subsoil. Approach the site supervisor.
• Ask for “clean fill” specifically — Always specify clean fill dirt with no construction debris, asphalt, concrete chunks, or contamination. Clean fill is what you want for residential grading.

Fill Dirt vs. Topsoil: Which One Do You Need?

This is the most important distinction in any grading project. Using fill dirt where you need topsoil — or topsoil where you need structural fill — is a costly mistake.

The correct system for a new lawn after major grading: fill dirt (compacted base to achieve grade) → 4–6 inches of screened topsoil → seed or sod. Skipping the topsoil cap and seeding directly into fill dirt results in thin, struggling grass at best and bare patches at worst.

For a detailed look at the topsoil cap step, see our guide on how much topsoil you need.

How Long Does Fill Dirt Take to Settle?

Properly compacted fill dirt that was placed in 6-inch lifts settles very little after the job — usually less than 1–2% over the first year. The compaction is what matters.

Uncompacted fill, on the other hand, can settle 10–20% or more over 1–3 years as the voids close on their own. This leads to sinkholes, unlevel lawns, cracked driveways, and in severe cases, foundation movement. If you can't rent a plate compactor, at minimum tamp each lift thoroughly with a hand tamper before adding the next layer.

For fill placed around tree stumps or organic debris: the organic material will decompose over years, causing ongoing settling. Remove stumps and large roots before filling whenever possible.

How to Compact Fill Dirt Correctly

1. Spread in 6-inch lifts. Never dump a full 2–3 ft layer and try to compact it all at once. The compactor only penetrates 6–8 inches effectively.
2. Compact each lift before adding the next. Make overlapping passes with the plate compactor — think mowing pattern, not random.
3. Moisture matters. Slightly damp soil compacts better than bone-dry or saturated soil. If the fill is very dry, lightly mist it before compacting.
4. Check your grade as you go.Don't wait until the final lift to check slope. Correct while material is still loose.
5. Cap with topsoil last. After all fill is compacted to your target grade, add your 4–6 inch topsoil layer before seeding or sodding.

Common Fill Dirt Mistakes

• Skipping the 15% compaction buffer: The most common calculation error. Your raw cubic yard number is never your order number. Multiply by 1.15.
• Using fill dirt as topsoil:Fill dirt has no nutrients. Grass and plants won't thrive without a topsoil cap. Budget for both materials.
• Accepting contaminated fill: Always ask for clean fill and inspect a load before accepting it. Fill with chunks of concrete, asphalt, or debris causes problems when you try to plant or pave later.
• Grading toward the foundation: Always slope fill away from any structure. The standard is 6 inches of drop over the first 10 feet from a foundation.
• Not accounting for settling near organics: If there are buried stumps, roots, or organic material under your fill area, they will decompose and cause sinkholes. Remove them or account for significant long-term settling.

Related Calculators

Planning the full project stack? These tools cover the next steps:

• Fill Dirt Calculator — instant cubic yard, ton, and truckload estimates
• Topsoil Calculator — calculate the growing layer that goes on top of fill dirt
• Sod Calculator— estimate sod rolls and cost after you've finished grading
• Gravel Calculator — if you need a gravel drainage layer or driveway base
• Cubic Yards Calculator — convert between cubic feet, cubic yards, and tons
• How Much Topsoil Do I Need? — depth guide and cost breakdown for the topsoil cap