Raised Bed Volume Calculator

Raised Bed Volume Planning

Raised beds improve soil structure and drainage, but they also require accurate volume planning to avoid under-ordering amendments. The total soil needed depends on the bed’s footprint and depth. For rectangle beds, the calculation is straightforward: length × width × depth. Circular beds are calculated using \(\pi r^2\). L-shaped beds are best modeled as a large rectangle with a smaller rectangle removed. Converting the resulting cubic volume into cubic yards or liters makes it easy to compare with bulk soil deliveries or bagged soil products.

This calculator provides results in cubic feet, cubic yards, and liters to support both imperial and metric gardeners. It also estimates bag counts using common sizes (1.5 ft³ or 40 L) so you can price out soil blends and compost. Remember that organic material and potting mixes settle after watering, so it’s often wise to order 10–15% extra to top up the bed after the first few waterings. This is especially important for deep beds or for homesteading operations where high organic matter is desired.

Use this tool for garden planning, raised bed expansions, or soil amendment projects. If you are blending compost and topsoil, compute the total volume and then apply your desired mix ratio (for example, 60% topsoil, 30% compost, 10% perlite). Combined with seeding rate and irrigation tools, this helps optimize both plant health and resource efficiency.

Soil volume is not the same as soil weight. Bulk density varies with texture and moisture, so a cubic foot of compost weighs less than a cubic foot of damp topsoil. If you need to calculate delivery weight for a trailer or truck, check supplier density charts. Also consider layering: some gardeners fill the lower portion with logs or coarse organic matter (hugelkultur) to reduce cost and improve long-term moisture retention. Account for those layers in the depth so the final soil surface is still at the target planting height.

Formula

Rectangle: \(V = L \times W \times D\). Circle: \(V = \pi r^2 D\). L-shape: \(V = (L \times W - L_c \times W_c) \times D\). Volume conversions: \(1\,\text{yd}^3 = 27\,\text{ft}^3\), \(1\,\text{ft}^3 = 28.3168\,\text{L}\).

Example Calculation

A rectangular bed 8 ft by 4 ft at 12 inches deep is 8 × 4 × 1 = 32 ft³. That is 1.19 yd³ and about 906 liters. At 1.5 ft³ per bag, you need roughly 22 bags.

FAQs

What soil volume should I use?

Use finished bed dimensions and depth. Include compost layers in the total depth.

How do I estimate bag counts?

Divide cubic feet by 1.5 ft³ or liters by 40 L to estimate bag counts.

Does this include settling?

No. Add 10–15% extra for settling after watering.

Can I use metric units?

Yes. Switch units to meters and centimeters for dimensions and liters for volume.

Are results private?

Yes, everything runs locally in your browser.

How it works

This calculator applies geometric volume formulas and converts to common soil units. All computation runs client-side for privacy and speed.

Disclaimer

Bag counts and volumes are estimates. Add extra volume for settling and follow soil product guidance.