Raised Garden Bed Calculator
Calculate the soil volume, lumber, and hardware needed to build your raised garden bed from scratch.
How to Calculate Raised Garden Bed Materials
Start with your bed dimensions: multiply length × width × height to get the volume in cubic feet, then convert to cubic yards (divide by 27). For lumber, you need boards for all four sides — the number of board rows depends on your bed height divided by the board width. Always add corner posts for structural support, especially for beds taller than 12 inches.
Popular Raised Bed Sizes
| Size | Soil Needed | Best For |
|---|---|---|
| 4×4 ft × 12 in | ~0.6 cubic yards | Small gardens, herbs, salad greens |
| 4×8 ft × 12 in | ~1.2 cubic yards | Most popular size — vegetables, flowers |
| 4×8 ft × 24 in | ~2.4 cubic yards | Root vegetables, accessibility (less bending) |
| 3×6 ft × 18 in | ~1.0 cubic yards | Compact spaces, patios |
Choosing the Right Wood
Cedar and redwood are the best choices for raised beds — they're naturally rot-resistant and can last 10–15 years without treatment. Pressure-treated pine is cheaper and lasts even longer, but some gardeners prefer untreated wood for growing food (modern PT lumber uses copper-based preservatives considered safe by the EPA for garden use). Avoid railroad ties, old pallets, and any wood treated with creosote or CCA.
Soil Mix Options
- Pre-mixed garden soil: Easiest option. Buy bags of raised bed mix from your garden center.
- Mel's Mix: Equal parts compost, peat moss, and vermiculite. Excellent drainage and nutrients. Best for square foot gardening.
- 60/40 blend: 60% topsoil and 40% compost. Most economical for large beds. Order in bulk (by the cubic yard) for big savings.
Tips for Your Raised Bed Project
- Keep beds no wider than 4 feet so you can reach the center from either side without stepping in.
- Place beds in a spot that gets at least 6–8 hours of direct sunlight for vegetables.
- Line the bottom with hardware cloth (1/2 in mesh) to keep out moles and gophers.
- Leave 2–3 feet between beds for walking, kneeling, and wheelbarrow access.
- Fill the bottom third of deep beds (18 in+) with logs, branches, or straw to save on soil (hugelkultur method).
- Buying soil in bulk (by the cubic yard from a landscape supply) is 50–70% cheaper than bagged soil for beds over 4×8.
Frequently Asked Questions
A 4x8 foot raised bed that is 12 inches deep needs 32 cubic feet of soil, or about 1.2 cubic yards. That equals sixteen 2-cubic-foot bags of soil. For a budget-friendly option, fill the bottom third with logs, branches, or straw, then fill the rest with soil mix. Buying soil in bulk (by the cubic yard) is 50-70% cheaper than bagged for larger projects.
Cedar is the top choice for raised beds because it is naturally rot-resistant and lasts 10-15 years without chemical treatment. Redwood is equally durable but more expensive and harder to find. Pressure-treated pine is the most affordable and lasts the longest, and modern copper-based treatments are considered safe by the EPA for growing food. Avoid railroad ties, pallets, and any CCA-treated wood.
Most vegetables grow well in 12 inches of soil depth, making it the most popular choice. Shallow-rooted plants like lettuce and herbs can grow in 6 inches. Root vegetables like carrots and potatoes need 18-24 inches. If your raised bed sits on concrete or poor soil, aim for at least 18 inches to give roots adequate space.
A popular all-purpose mix is 60% topsoil and 40% compost. For square foot gardening, try Mel's Mix — equal parts compost, peat moss, and vermiculite. For a budget option, use bulk garden soil from a landscape supply and amend with compost. Avoid using only native soil from your yard, as it is usually too compacted and lacks nutrients for raised bed growing.
A basic 4x8-foot cedar raised bed costs $75-$150 in lumber and hardware for a 12-inch-tall bed. Soil adds $40-$80 if using bags, or $30-$50 in bulk. Total DIY cost is typically $120-$230 per bed. Pressure-treated pine cuts lumber costs roughly in half. Pre-made raised bed kits range from $50-$300 but offer convenience.