Soil Volume Calculator
Compute soil volume, weight, or required truckloads from rectangular/circular areas or known area × depth. Units convert automatically.
Practical Guide
Soil Volume Calculator: Fast, Accurate Yardage for Beds, Planters, and Lawns
Use this guide to turn project dimensions into cubic yards, cubic feet, or liters—then convert to bag counts or truck loads. We cover shapes, recommended depths, compaction/settlement allowances, and worked examples in US and metric units.
Quick Start
- 1 Measure the area and desired finished depth. Keep units consistent (all ft/in or all m/mm).
- 2 Pick a shape method: Rectangle \(V = L \times W \times D\), Circle \(V = \pi r^2 D\), or Custom via total area \(V = A \times D\).
- 3 Add a settlement allowance (typically 10–20% for loose topsoil/garden mix).
- 4 Convert units as needed: \(1~\text{yd}^3 = 27~\text{ft}^3\), \(1~\text{m}^3 = 1000~\text{L}\). Turn cubic yards into bag counts or truck loads.
- 5 Round up to whole bags or a safe fractional yard (e.g., 0.25 yd³ increments) before ordering.
Tip: For new beds, 4–6 in of soil is typical. For raised beds, 8–12 in is common. For lawn topdressing, 0.25–0.5 in is plenty.
Watch out: Moist soils are heavier and settle more. If your supplier sells by compacted yard, your loose-fill calculator result may need extra to match delivered density.
Variables & Symbols
- L length
- W width
- D depth (thickness)
- A plan area
- r radius (for circles)
- V volume
Choosing an Approach
Method A — By Dimensions (Rectangles/Strips)
Great for garden beds, pathways, or raised planters with straight edges.
- Simple inputs; easy to double-check on site.
- Works well for multiple repeated beds.
- Directly returns ft³/yd³ without intermediate area math.
- Less ideal for curved/irregular spaces.
- Missed corners or cutouts can overstate volume.
Rectangle: \(V = L \times W \times D\)
Method B — By Total Area (Any Shape)
Best when you already know the surface area or have curves/irregular edges.
- One depth multiplied by total area covers any plan shape.
- Easy to use with plan takeoffs from CAD or a wheel.
- Relies on accurate area measurement.
- Varied depth zones require splitting into sub-areas.
Any shape: \(V = A \times D\)
What Moves the Number the Most
Depth choice
Small changes in depth swing volume quickly. Doubling depth doubles volume.
Settlement allowance
Loose topsoil can settle 10–20% after watering/traffic. Add a percentage to avoid thin spots.
Unit conversions
Keep units consistent. Mix-ups (in vs ft, mm vs m) cause the largest errors.
Shape assumptions
Approximating curves as rectangles usually overestimates; use area-based input for arcs.
Bulk density
Heavier clay/compost-rich mixes behave differently than sandy loam; delivery is often by volume, not weight.
Voids & structures
Raised beds with internal braces, rocks, or irrigation manifolds reduce fill volume; subtract these volumes.
Worked Examples
Example 1 — US Units (Rectangular bed, settlement included)
- Bed size: \(L=24~\text{ft}\), \(W=5~\text{ft}\)
- Depth: \(D=6~\text{in}=0.5~\text{ft}\)
- Allowance (settlement): 15%
- Bag size for comparison: 2 ft³
1
Compute volume in ft³: \[V = L \times W \times D = (24)(5)(0.5)=60~\text{ft}^3\]
2
Convert to yd³: \[V_{\text{yd}^3}=\dfrac{60}{27}=2.222…\approx 2.22~\text{yd}^3\]
3
Add 15% allowance: \[2.22 \times 1.15 = 2.553 \approx 2.56~\text{yd}^3\]
4
Bag equivalent (2 ft³): \[\dfrac{60 \times 1.15}{2} = 34.5 \Rightarrow \text{order } 35 \text{ bags}\]
If ordering bulk, round to the supplier’s increment (e.g., 2.75 or 3.0 yd³) based on truck capacity and budget.
Example 2 — Metric (Circular planter, area method)
- Planter diameter: \(d=2.4~\text{m}\Rightarrow r=1.2~\text{m}\)
- Depth: \(D=0.25~\text{m}\)
- Allowance: 10%
- Bag size for comparison: 40 L
1
Area: \[A=\pi r^2 = \pi(1.2)^2 \approx 4.524~\text{m}^2\]
2
Volume: \[V = A \times D = 4.524 \times 0.25 \approx 1.131~\text{m}^3\]
3
Add 10%: \(1.131 \times 1.10 = 1.244~\text{m}^3\)
4
Convert to liters: \(1.244~\text{m}^3 \times 1000 = 1244~\text{L}\Rightarrow \frac{1244}{40}\approx 31.1 \Rightarrow 32 \text{ bags}\)
To convert to yd³, use \(1~\text{m}^3 = 1.308~\text{yd}^3\).
Common Layouts & Depth Guidelines
Depth drives volume. Use industry-typical ranges below, then adjust for your plantings and soil type.
| Use Case / Layout | Typical Depth | Allowance | Notes |
|---|---|---|---|
| New planting bed (ornamentals) | 4–6 in (100–150 mm) | 10–15% | Blend with existing soil; deeper for large shrubs. |
| Vegetable raised bed | 8–12 in (200–300 mm) | 10–20% | Use garden mix (topsoil + compost). Consider seasonal settling. |
| Lawn topdressing | 0.25–0.5 in (6–12 mm) | 5–10% | Thin, even layers; brush into turf canopy. |
| Tree rings / circular beds | 3–4 in (75–100 mm) | 10–15% | Keep soil away from trunk flare; avoid volcano mounding. |
| Pathways & strips (soil base before sod) | 2–4 in (50–100 mm) | 10–15% | Check final grades and drainage slopes. |
- Confirm depth after watering-in; top up thin sections.
- Split irregular areas into simple shapes to reduce overestimation.
- Subtract internal volumes (posts, rocks, planter fixtures).
- Pick a single unit system; convert once at the end.
Buying & Logistics
1) Product Selection
- Topsoil vs. garden mix: Garden mix (with compost) is better for vegetables and annuals.
- Screened vs. unscreened: Screened soils are consistent and easier to spread.
- pH & organic matter: Ask supplier for basics if planting sensitive species.
2) Delivery & Handling
- Bulk trucks often deliver in ~1/2–1 yd³ increments; small dump trailers vary.
- Protect adjacent surfaces; wet soil stains paving.
- Stage near the work; wheelbarrow distance drives labor hours.
3) Sanity Checks
- Does the yardage align with similar past projects?
- If curves dominate, did you use the area method?
- Did you include settlement? Round up rather than risk shortages.
Regional notes: Local codes may restrict soil placement over utilities or against foundations; verify setbacks and drainage requirements.
Frequently Asked Questions
How do I convert cubic feet to cubic yards?
Divide by 27. One cubic yard equals 27 cubic feet, so \( \text{yd}^3 = \frac{\text{ft}^3}{27} \).
What settlement allowance should I use?
For loose topsoil or garden mixes, plan on 10–20% settlement after watering and traffic. Use the higher end for deep fills or very organic mixes.
How many 2-ft³ bags are in a cubic yard?
\(1~\text{yd}^3 = 27~\text{ft}^3\). With 2-ft³ bags, \( \frac{27}{2} = 13.5 \). Round up to 14 bags per yard equivalent (not accounting for settlement).
What depth should I use for a new garden bed?
Most ornamental beds perform well at 4–6 in (100–150 mm). Vegetable beds often use 8–12 in (200–300 mm), especially in raised planters.
How do I calculate soil for a circular bed?
Use area \(A=\pi r^2\) with radius \(r=d/2\) and multiply by depth \(D\): \(V=\pi r^2 D\). Ensure depth is in the same units as radius.
Should I account for obstacles inside a raised bed?
Yes. Subtract the volume of internal braces, large rocks, irrigation manifolds, or planter reservoirs to avoid over-ordering.