Topsoil Calculator
By Concrete Knowhow Editorial Team · Updated July 2026 · 7 min read
Quick Answer
Length
Width
Depth
Settling Allowance
Topsoil compacts 10–15% after delivery. Order extra so you end up at your target depth, not short.
Common Coverage Areas: Quick Reference
“Order This Much” includes a 10% settling allowance.
| Area | Depth | Cubic Yards | Order This Much |
|---|---|---|---|
| 10×10 ft | 2" | 0.62 yd³ | 0.68 yd³ |
| 10×10 ft | 4" | 1.23 yd³ | 1.36 yd³ |
| 10×20 ft | 4" | 2.47 yd³ | 2.72 yd³ |
| 10×20 ft | 6" | 3.70 yd³ | 4.07 yd³ |
| 20×20 ft | 4" | 4.94 yd³ | 5.44 yd³ |
| 20×40 ft | 4" | 9.88 yd³ | 10.86 yd³ |
| 50×50 ft | 6" | 46.30 yd³ | 50.93 yd³ |
Topsoil, Garden Soil, Compost, or Fill Dirt: Which One Do You Need?
Suppliers sell several soil products that look similar in a pile but behave very differently. Ordering the wrong one is a common and expensive mistake.
| Product | What It Is | Use It For | Do Not Use It For |
|---|---|---|---|
| Screened topsoil | Native surface soil, screened for rocks and debris | New lawns, grading, filling low spots in turf | Containers, raised beds on their own |
| Garden soil | Topsoil blended with compost or other organics | Planting beds, vegetable gardens | Structural fill or grading |
| Compost | Fully decomposed organic matter | Amending existing soil, topdressing lawns | Filling depth on its own; it keeps shrinking as it decomposes |
| Fill dirt | Subsoil with little or no organic matter | Raising grade, filling holes, building up slopes | Anything you want plants to grow in |
The standard money-saving approach for deep fills: use fill dirt for everything below the top 4 to 6 inches, then finish with screened topsoil. Fill dirt typically costs a third to half as much per yard.
How the Topsoil Math Works
Length times width times depth (in feet) gives cubic feet; divide by 27 for cubic yards. The step people miss with soil is the settling allowance. Bulk topsoil is fluffed up by screening and loading, and it compacts 10 to 15 percent once it is watered and walked on. The calculator adds that allowance to the order quantity.
Worked example. Topdressing a 25 ft by 30 ft lawn area with 3 inches of soil: 25 times 30 times 0.25 equals 187.5 cubic feet, or 6.94 cubic yards. With a 10 percent settling allowance, order about 7.6 yards, which most suppliers round to 8. At 1,800 to 2,200 pounds per dry cubic yard, that load weighs roughly 7 to 9 tons, so it arrives on a full-size dump truck. Plan a driveway spot for the pile, and put a tarp down first: cleanup is far easier and you lose less soil to the lawn.
How to Spread Topsoil, Step by Step
- Test your existing soil. A basic soil test (available at garden centers) tells you pH and nutrient levels. Amend existing soil before adding topsoil where possible, since that is cheaper than replacing it.
- Remove debris and weeds. Clear the area of rocks, roots, and existing vegetation. Till or loosen compacted areas to at least 4 inches to help new topsoil blend with native soil.
- Calculate and order. Use this calculator and add 10–15% for settling. Have it delivered as close to the project area as possible, because topsoil is heavy to move by hand.
- Spread and grade. Distribute topsoil evenly with a rake. Work toward a slight slope away from foundations (6 inches per 10 feet) to direct drainage away from structures.
- Till the interface. Where new topsoil meets existing soil, till 2–3 inches deep to blend the layers. This prevents a hard boundary that can trap water or restrict root growth.
- Compact lightly. Use a lawn roller or your feet to gently firm the surface. Avoid heavy compaction: you want soil to be firm but still have air pockets for root development.
- Water thoroughly. Water the new topsoil to encourage settling and help it bond with underlying soil. You may need to top up low spots.
- Seed, sod, or plant. Wait 1–2 days after watering before seeding or laying sod so the surface firms up slightly. New plantings should be watered daily for the first 2 weeks.
Frequently Asked Questions
- How much topsoil do I need for a 10×20 ft lawn area at 4 inches deep?
- A 10×20 ft area at 4 inches deep is 66.7 cubic feet, about 2.47 cubic yards. With a 10% settling allowance, order 2.72 cubic yards to end up at your target depth after compaction.
- How deep should topsoil be for a new lawn?
- Grass roots need at least 4–6 inches of good topsoil. For a new lawn from seed or sod, aim for 4 inches minimum; 6 inches is better in compacted or poor native soil. Raised garden beds typically need 8–12 inches.
- Why do I need to order extra topsoil for settling?
- Bulk topsoil is loose when delivered and compacts 10–15% once watered in, walked on, and settled over time. If you order only the exact calculated amount, you will end up short of your target grade. Always add 10–15%.
- How much does a cubic yard of topsoil weigh?
- A cubic yard of dry topsoil weighs roughly 1,800–2,200 lbs depending on its composition and moisture content. Wet topsoil can weigh over a ton per cubic yard.
- What is the difference between topsoil and fill dirt?
- Topsoil is the upper 2–8 inches of earth, rich in organic matter and nutrients, and it supports plant growth. Fill dirt is subsoil used to fill voids or raise grade, contains little organic matter, and should never be used as a growing medium.
- How many bags of topsoil equal a cubic yard?
- A standard 40 lb bag of topsoil is about 0.75 cubic feet. You need approximately 36 bags to equal one cubic yard (27 ft³). Bulk delivery is far more economical for any project over 1–2 cubic yards.