Soil Calculator

Calculate how much soil you need for your garden or yard

Enter the dimensions of your area and soil density to calculate the required volume and weight of topsoil, along with the estimated cost.

Last updated: 2026-07-22

CreatorFrank Zhao

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Introduction / overview

Whether you are filling a raised garden bed, levelling a patch of lawn, or ordering bulk topsoil for a landscaping project, the hardest part is often figuring out how much you actually need. Too little and you are making another trip to the garden centre; too much and you are stuck with a pile of dirt you will never use.

The Soil Calculator takes the guesswork out of the equation. Enter the length and width of your area (or the area directly), choose how deep you want the soil layer to be, and optionally add the soil density to get the total weight. If you are shopping by price, you can also add a cost per unit of mass or volume and see your total instantly. Every field is connected, so changing any value automatically recalculates the rest.

✅ Whether you are a weekend gardener, a landscape contractor, or a DIY homeowner, this tool saves you from over-ordering or running short. It handles metric and imperial units, supports multiple currencies, and works just as well for topsoil, compost, or fill dirt.

Who is this for?

Home gardeners working out how much topsoil or compost to buy for flower beds or vegetable patches.
Landscapers and contractors estimating bulk material orders for residential or commercial projects.
DIY homeowners levelling a yard, filling a play area, or installing a new garden bed.

If you are working on a raised bed specifically, check out our Raised Bed Soil Calculator for predefined soil mix recipes. For laying a new lawn, the Sod Calculator helps you estimate rolls and cost.

How to use / quick start

1Enter the area dimensions. Type in the Length and Width of the surface you want to cover. You can switch units (meters, feet, yards, etc.) using the dropdown next to each field. If you already know the area, you can enter it directly in the Area field instead.
2Set the desired depth. How thick do you want the soil layer? For a flower bed, 15–30 cm (6–12 inches) is typical; for a lawn topdressing, 2–5 cm (1–2 inches) is enough. The default unit is centimetres.
3Add the soil density (optional). If you know the density from the bag label or a supplier's data sheet, enter it. Common topsoil has a density around 1,200–1,700 kg/m³. This lets the calculator estimate the total weight, which is useful when you are ordering by the ton.
4Enter pricing (optional). If you want a cost estimate, fill in Price per unit massor Price per unit volume. You can choose the currency and the mass/volume unit independently.
5Read your results. The Volume needed, Weight needed, and Total costfields update automatically as you type. You can edit any result to work backwards — for example, enter a target cost to see what volume or depth you would need.

Example: filling a 4 m × 2 m flower bed

Length = 4 m, Width = 2 m → Area = 8 m²
Depth = 25 cm (0.25 m) → Volume = 2 m³
Density ≈ 1,400 kg/m³ → Weight ≈ 2,800 kg (2.8 metric tons)
If soil costs $50 per metric ton → Total ≈ $140

Real-world examples

1. Topdressing a lawn

The situation: Your front lawn measures roughly 10 m long by 6 m wide, and it has developed some uneven spots. You want to spread a thin layer of topsoil (about 3 cm deep) to level it out before overseeding. The local garden centre sells topsoil by weight at $60 per metric ton, and you estimate the bulk density at about 1,500 kg/m³.

Calculator inputs:

Length = 10 m, Width = 6 m
Depth = 3 cm
Density = 1,500 kg/m³
Price per unit mass = $60 / t (SGD)

Results:

Area = $10 \times 6 = 60\ \text{m}^2$
Volume = $60 \times 0.03 = 1.8\ \text{m}^3$
Weight = $1.8 \times 1500 = 2,700\ \text{kg}$ = 2.7 t
Total cost = $2.7 \times 60 = \$162$

How to apply: You'll need about 2.7 metric tons of topsoil, costing roughly $162. Spread it evenly over the lawn and rake it smooth before seeding. For the seeding itself, consider our Sod Calculator if you prefer laying turf instead.

2. Ordering compost for community gardens

The situation: A community garden club is refreshing the soil in 12 raised beds. Each bed measures 2.4 m × 1.2 m, and they want a 20 cm layer of fresh compost. The local supplier sells compost in cubic metres at $45/m³. They also want to know the total cost to plan the budget.

Calculator inputs (per bed):

Length = 2.4 m, Width = 1.2 m
Depth = 20 cm
Price per unit volume = $45 / m³ (SGD)

Results:

Area per bed = $2.4 \times 1.2 = 2.88\ \text{m}^2$
Volume per bed = $2.88 \times 0.2 = 0.576\ \text{m}^3$
Total volume = $0.576 \times 12 = 6.912\ \text{m}^3$
Total cost = $6.912 \times 45 \approx \$311$

How to apply: Order about 7 m³ of compost and budget around $311. The garden club can split the cost among members. Mixing in compost with existing soil improves texture and nutrient content — our Compost Calculator has more details on compost applications.

3. Budgeting a landscaping project

The situation: A homeowner wants to turn a 15 m × 8 m backyard corner into a planting area with a 40 cm deep soil bed. The contractor quoted $85 per cubic yard of fill. The homeowner wants to check whether they can stay within a $1,500 budget. They know the fill density is about 1,600 kg/m³.

Calculator inputs:

Length = 15 ft, Width = 8 ft
Depth = 40 cm → ~15.75 inches
Price per unit volume = $85 / cu yd (SGD)

Results:

Area = $15 \times 8 = 120\ \text{ft}^2$
Volume = $120 \times 15.75 / 12 = 157.5\ \text{cu ft}$ ≈ $5.83\ \text{cu yd}$
Total cost = $5.83 \times 85 \approx \$496$

How to apply: The project costs around $496, well under the $1,500 budget. The homeowner can either increase the depth, expand the area, or save the remaining budget for plants and irrigation. The calculator's bidirectional engine lets you experiment: try entering your target cost to see what volume or area that budget would allow.

Common scenarios

Measuring irregular areas

Not every garden is a perfect rectangle. If your yard has an L-shape or includes a patio, split it into smaller rectangles, calculate each one separately, and add the volumes together. The calculator handles rectangular areas natively, so a little planning goes a long way.

Pro tip: Use the Area field directly if you have already measured the total area with a tape measure or a garden planner app.

Bulk vs bagged soil

Bulk soil is sold by the cubic yard or metric ton and is usually cheaper for large projects. Bagged soil is sold by volume (cubic feet or litres) and is more convenient for small gardens. Use the weight result to compare bulk pricing with the cost of individual bags.

Pro tip: In the Price per unit mass field, you can switch to "kg" or "lb" pricing to match bag labels exactly.

Mix recipes and amendments

Many gardeners mix topsoil with compost, peat moss, or perlite in specific ratios (e.g., 60:30:10). Calculate the total volume first with this tool, then split it by ratio to know how much of each ingredient to buy. Our Raised Bed Soil Calculator has built-in mix recipes if you are filling a raised bed.

Working backwards from a budget

Have a fixed budget? Enter your target cost in the Total cost field and the calculator will work backwards to show you what volume (and therefore what area and depth) that budget can buy. This is great for planning constraints before you start digging.

Tips & best practices

Getting the density right

The density of soil varies significantly depending on moisture content and composition. Dry topsoil is roughly 1,200–1,400 kg/m³, while damp, compacted soil can reach 1,700 kg/m³ or more. If you are unsure, ask your supplier for the typical density of their material, or use 1,500 kg/m³ as a reasonable middle-ground estimate.

Always add a little extra

Soil settles after being spread and watered. It is common practice to order 5–10% more than the calculated volume to account for compaction, spillage, and uneven surfaces. If your calculated volume is 2 m³, consider ordering 2.1–2.2 m³ in practice.

Check your measurements twice

A small measurement error can multiply into a significant volume difference. Measure each dimension twice, especially for large areas. The calculator is only as accurate as the numbers you put in — garbage in, garbage out.

Use the same units consistently

While the calculator handles unit conversion automatically, it is easy to accidentally mix up feet and inches or metres and centimetres. Stick to one unit system (metric or imperial) for all inputs to avoid confusion. The volume and weight results will automatically match whatever units you choose.

Calculation method / formulas

The Soil Calculator chains together a few straightforward relationships. Each formula works in both directions, so you can enter any combination of values and the tool fills in the rest.

Area

A = L \times W

The area of a rectangular surface is the product of its length and width. You can also enter the area directly if you already know it.

Volume

V = A \times D

Multiply the surface area by the desired soil depth to get the total volume needed.

Weight

W = \rho \times V

Weight is volume times density ( $\rho$ ). This is useful when suppliers charge by weight rather than volume.

Total cost (two ways)

C = W \times P_m

C = V \times P_v

You only need to fill one price field — either price per unit mass ( $P_m$ ) or price per unit volume ( $P_v$ ). The cost is calculated from whichever price you enter.

Variable reference

L

Length

W

Width

A

Area

D

Depth

V

Volume

\rho

Density

W

Weight

P_m

Price / mass

P_v

Price / volume

C

Total cost

Related concepts

What is topsoil, anyway?

Topsoil is the uppermost layer of the earth's surface, typically the top 5–30 cm (2–12 inches). It contains a mix of sand, silt, clay, and organic matter. Good-quality topsoil is dark, crumbly, and rich in nutrients — the foundation for healthy plant growth. When buying topsoil, look for a dark brown colour and a loose, friable texture that crumbles easily in your hand.

Bulk density explained

Soil bulk density is the weight of dry soil divided by its total volume (including pore spaces). It tells you how compacted the soil is. Low bulk density (1,000–1,300 kg/m³) means loose, well-aerated soil — great for roots. High bulk density (1,600+ kg/m³) indicates compaction, which restricts root growth and drainage. Most garden topsoil sits around 1,400–1,600 kg/m³. If your soil feels heavy and dense, adding compost or organic matter can lower the bulk density over time.

Why depth matters

Different plants need different soil depths. Shallow-rooted vegetables like lettuce and herbs thrive in 15–20 cm of soil. Deep-rooted plants like tomatoes, carrots, and shrubs need 30–45 cm or more. Lawns need only 10–15 cm of quality topsoil. Always check the root depth requirements of your specific plants before ordering soil — too shallow and growth will be stunted; too deep and you are wasting money.

Frequently asked questions

How many bags of topsoil do I need?

First, calculate the total volume using the calculator. Then divide by the volume per bag. For example, if you need 1 m³ of soil and each bag contains 0.75 cu ft (about 0.021 m³), you will need roughly $1 / 0.021 \approx 48$ bags. Most bag labels state the volume in cubic feet or litres — make sure to match the units.

How much area does a ton of topsoil cover?

It depends on the depth. A metric ton of typical topsoil (density ~1,500 kg/m³) has a volume of about $1000 / 1500 \approx 0.67\ \text{m}^3$ spread over an area of about $0.67 / 0.1 = 6.7\ \text{m}^2$ at 10 cm deep, or $0.67 / 0.05 = 13.4\ \text{m}^2$ at 5 cm deep. Enter your numbers into the calculator to get a precise answer for your specific situation.

Can I use this calculator for compost or mulch?

Absolutely. The calculator works for any bulk material — topsoil, compost, mulch, sand, or gravel. Just adjust the density to match the material. Compost is lighter (around 600–800 kg/m³) while sand is heavier (around 1,600–1,800 kg/m³). For dedicated compost calculations, check out our Compost Calculator.

What if my garden area isn't a rectangle?

Break it into smaller rectangular sections, calculate each one, and add the volumes together. For circular beds, measure the radius and calculate the area using $\pi r^2$ , then enter it directly in the Area field. For triangular sections, use $\frac{1}{2} \times \text{base} \times \text{height}$ .

Does the calculator account for soil settling?

Not automatically — the calculator gives you the loose volume. Soil settles by roughly 5–15% after watering and time. It is a good idea to order about 10% extra to account for this. For example, if the calculator says you need 2 m³, consider ordering 2.2 m³.

Why does the total cost field change when I edit volume or weight?

Because all the fields are interconnected. The cost is calculated from whichever price you entered (per mass or per volume). If you edit the volume or weight directly, the cost updates to match. Similarly, if you edit the cost, the calculator works backwards to show you what volume or mass your budget can afford. This works for every field — try it!

Limitations & disclaimers

Important notes

Not a replacement for professional surveying. For large-scale projects, always have a contractor or landscape architect verify measurements and material estimates on site.
Density varies. The calculator uses whatever density you enter. Moisture content, compaction, and material composition all affect real-world density. Check with your supplier for the most accurate figure.
Currency rates are indicative. Exchange rates update periodically but may not reflect the very latest market rate. Verify pricing with your supplier before committing to a purchase.
Not financial or legal advice. Cost estimates are for planning purposes only. Always get a written quote from your material supplier before ordering.

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