Raised Bed Soil Calculator
The Raised Bed Soil Calculator computes interior volume accounting for wall thickness, then breaks down the soil into component volumes for 5 mix recipes including Mel's Mix and Hügelkultur. SVG composition chart and cross-section diagram — features an AI chatbot cannot replicate. Free, no sign-up required.
Bed Size Presets
Bed Dimensions
Results
Interior Dimensions
Length
7.75 ft
Width
3.75 ft
Interior Area
29.06 ft² / 2.7 m²
Total Volume
cu ft
29.06ft³
cu yd
1.08yd³
L
823L
Total Weight
lbs
1,776 lbs
kg
805 kg
Bag Counts
1 cu ft bags
30
2 cu ft bags
15
40 L bags
21
Lumber (board feet)
~144 bf
Soil Mix Composition
Bed Cross Section
Soil Mix Recipes
| Mix | Components | Description |
|---|---|---|
| Standard Mix | Topsoil 60%, Compost 30%, Perlite/Vermiculite 10% | 60% topsoil, 30% compost, 10% perlite/vermiculite |
| Mel's Mix | Compost (blended) 33.3%, Peat Moss 33.3%, Vermiculite 33.4% | 1/3 compost, 1/3 peat moss, 1/3 vermiculite |
| Hügelkultur Style | Logs/Branches 40%, Compost 30%, Topsoil 20%, Mulch Top Layer 10% | 40% logs/branches, 30% compost, 20% topsoil, 10% mulch |
| Sandy/Well-Draining | Topsoil 40%, Coarse Sand 30%, Compost 20%, Perlite 10% | 40% topsoil, 30% coarse sand, 20% compost, 10% perlite |
| Custom Mix | Topsoil 50%, Compost 30%, Amendment 20% | Define your own topsoil/compost/amendment ratios |
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What is a Raised Bed Soil Calculator?
A raised bed soil calculator determines the interior volume of a raised garden bed after accounting for wall thickness, then breaks that volume into individual soil components based on your chosen mix recipe. Popular recipes include the Standard Mix (60% topsoil, 30% compost, 10% perlite) and Mel's Mix (equal parts compost, peat moss, and vermiculite). The calculator provides bag counts, weight estimates, and cost projections.
How to Use This Calculator
- Select a bed size preset or enter custom dimensions
- Choose the bed material — wall thickness is auto-calculated
- Select a soil mix recipe (Standard, Mel's Mix, Hügelkultur, Sandy, or Custom)
- For custom mixes, adjust the topsoil/compost/amendment percentages
- Optionally enter a price per cubic yard for cost estimation
- Review the volume, component breakdown, bag counts, and cost
Frequently Asked Questions
How much soil do I need for a 4×8 raised bed that is 12 inches deep?
A 4×8 ft bed at 12 inches deep with 1.5-inch wood walls has an interior of about 31 cubic feet or 1.15 cubic yards. That is roughly 16 standard 2 cu ft bags of soil mix. At $30–40 per cubic yard for bulk delivery, expect to spend $35–46.
What is Mel's Mix and is it worth the cost?
Mel's Mix is the soil formula from Square Foot Gardening: equal parts blended compost, peat moss, and vermiculite. It is lightweight, nutrient-rich, and well-draining. It costs more than basic topsoil but produces excellent results in raised beds. A 4×8 bed needs about 10 cubic feet each of the three components.
Should I fill the entire raised bed with soil?
For beds over 18 inches tall, consider Hügelkultur: fill the bottom 40% with logs, branches, and yard waste, then top with compost and soil. This saves money, improves drainage, and creates a self-fertilizing bed as the wood decomposes over years.
How much does raised bed soil weigh?
Weight varies by mix: a standard topsoil mix weighs about 78 lbs per cubic foot, while Mel's Mix weighs about 22 lbs per cubic foot. A 4×8×12 inch bed holds roughly 2,400 lbs of standard mix or 680 lbs of Mel's Mix. Consider this when placing beds on decks or rooftops.