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Calculate soil, lumber, and hardware for raised garden beds
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A raised bed calculator helps you determine the exact amount of soil, lumber, and hardware needed to build raised garden beds. Whether you're planning a single vegetable bed or multiple planting areas, this tool ensures you purchase the right quantities.
Raised beds offer numerous advantages over in-ground planting: better drainage, warmer soil in spring, easier weed control, and the ability to customize soil composition. The calculator accounts for:
Example: 4 ft × 8 ft × 1 ft = 32 cubic feet ÷ 27 = 1.19 cubic yards
Example: 4×8 bed, 2 courses = (2 × 12) × 2 = 48 linear feet
The best raised bed soil combines three key components for optimal plant growth:
Provides structure, minerals, and microbial life. Use quality screened topsoil.
Adds nutrients, beneficial organisms, and improves water retention.
Perlite or vermiculite improves drainage and prevents compaction.
Tip: This mix is often called "Mel's Mix" from the Square Foot Gardening method. Adjust ratios based on your plants—root vegetables prefer more aeration.
| Size | Best For | Soil (12") | Lumber |
|---|---|---|---|
| 4×4 ft | Small spaces, herbs | 0.6 cu yd | 32 ft |
| 4×8 ft | Most popular, versatile | 1.2 cu yd | 48 ft |
| 3×6 ft | Easy reach, tight spaces | 0.7 cu yd | 36 ft |
| 4×12 ft | Large gardens, rows | 1.8 cu yd | 64 ft |
| 2×8 ft | Narrow spaces, paths | 0.6 cu yd | 40 ft |
Keep width to 4 feet maximum so you can reach the center from either side. Longer beds may need mid-span supports.
Naturally rot-resistant, lasts 10-20 years. No chemicals leaching into soil. Beautiful natural appearance. More expensive but worth it for food gardens.
Modern ACQ-treated lumber is safe for vegetables per EPA guidelines. Most economical option. Use with plastic liner if concerned.
Most vegetables need 6-12 inches of soil depth. Deep-rooted plants like tomatoes and carrots benefit from 12-18 inches. For accessibility or poor native soil, 18-24 inches is ideal.
Line the bottom with hardware cloth to keep out burrowing pests. Avoid landscape fabric which can impede drainage. Cardboard at the bottom will decompose and suppress weeds initially.
Cedar raised beds typically last 15-20 years in most climates. In very wet conditions, expect 10-15 years. The wood grays naturally but remains structurally sound.
Modern ACQ-treated lumber (used since 2003) is considered safe for vegetable gardens by the EPA. It contains copper, not arsenic like older CCA-treated wood.
Potting soil alone is expensive and may be too light. Mix it with topsoil and compost. A 60/30/10 mix of topsoil, compost, and aeration material works best for large beds.
Yes, 4×4 corner posts add stability and prevent boards from bowing outward under soil pressure. They're essential for beds over 6 inches tall.