How to calculate cubic feet of soil
Soil is sold by volume — cubic feet for bags, cubic yards for bulk deliveries. To order the right amount, calculate the cubic feet needed for your raised bed, garden, or planter, then convert to whatever unit your supplier uses. The formula is the same as any rectangular volume:
cubic feet = length × width × depth, with all measurements in feet.
Common raised-bed sizes
| Raised bed | Conversion factor | Worked example |
|---|---|---|
| 4 × 4 × 1 ft | 4 × 4 × 1 | 16 ft³ |
| 4 × 8 × 1 ft | 4 × 8 × 1 | 32 ft³ |
| 4 × 12 × 1 ft | 4 × 12 × 1 | 48 ft³ |
| 6 × 12 × 1 ft | 6 × 12 × 1 | 72 ft³ |
| 4 × 8 × 0.5 ft (6 in deep) | 4 × 8 × 0.5 | 16 ft³ |
| 4 × 8 × 1.5 ft | 4 × 8 × 1.5 | 48 ft³ |
How many bags of soil do I need?
Bagged soil comes in three common sizes:
- 1 cubic foot bags — most affordable potting and topsoil. 27 bags per cubic yard.
- 1.5 cubic foot bags — common for premium garden soil. 18 bags per cubic yard.
- 2 cubic foot bags — usually cheaper potting/raised-bed mix. 14 bags per cubic yard.
The calculator above shows bag counts for all three sizes side-by-side so you can comparison-shop.
Bagged versus bulk pricing
Bagged soil typically costs $4–8 per cubic foot at garden centers. Bulk delivery usually runs $25–45 per cubic yard ($0.93–$1.67 per ft³) but adds a $50–125 delivery fee. The break-even point sits at roughly 0.5–1 cubic yard. Below that, bagged wins on convenience and total cost; above that, bulk delivery is dramatically cheaper.
Worked examples
Example 1: A 4 × 8 ft raised bed, 12 inches deep
4 × 8 × 1 = 32 ft³ = 1.19 yd³. Bag count: 32 of the 1 ft³ bags, 22 of the 1.5 ft³ bags, or 16 of the 2 ft³ bags.
Example 2: Lawn topdressing, 1,000 ft² at 0.5 inch deep
1,000 × 0.0417 ≈ 41.7 ft³ = 1.54 yd³. Order 1.5 yards delivered.
Example 3: A round planter, 3 ft diameter × 2 ft deep
π × 1.5² × 2 ≈ 14.14 ft³. About 7 of the 2 ft³ bags.
Topsoil weight reference
- Loose dry topsoil: ~75 lbs per ft³ (~2,025 lbs per yd³)
- Compacted topsoil: ~100 lbs per ft³ (~2,700 lbs per yd³)
- Saturated wet topsoil: ~130 lbs per ft³ (~3,510 lbs per yd³)
Knowing the weight matters for delivery — most pickup trucks can safely carry 1 cubic yard of topsoil, but two yards of wet soil can exceed the rated payload.
Common mistakes to avoid
- Mixing units. Convert everything to feet before multiplying. Inches to feet: divide by 12. Yards to feet: multiply by 3.
- Forgetting settling. Loose-delivered soil settles 10–15% in the first weeks. Order a slight surplus or plan to top up later.
- Underestimating depth. Most garden vegetables need at least 12 inches of soil; root crops need 18+ inches.
- Confusing topsoil with potting mix. Topsoil contains clay and silt; potting mix is mostly peat and perlite. They serve different purposes and cost very different amounts.
Related concepts and calculators
Once you have your soil volume in cubic feet, the next steps are usually a unit conversion or a project-specific calculation:
- Cubic feet to cubic yards — bulk soil delivery is priced by the yard.
- Cubic feet to pounds — at 75 lb/ft³ for loose topsoil, useful for trailer load limits.
- Raised garden bed calculator — adds a depth picker and soil-mix recommendations.
- Mulch calculator — same workflow for the layer that goes on top of the soil.
- Common mistakes — depth in inches vs feet trips up most first-time orders.
Frequently asked questions
Related calculators
Calculate cubic feet of soil needed for any size raised garden bed.
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OpenConvert cubic feet to cubic yards instantly. 27 ft³ = 1 yd³.
Open