Raised Garden Bed Calculator
Plan your perfect raised bed garden with precise material and planting calculations
Safety Note: Wear protective gear when handling treated lumber or soil amendments. Some materials may require special handling precautions.
Gardener's Tip: For optimal root growth, aim for at least 12" soil depth. Deeper beds (18-24") are better for root vegetables.
Bed Dimensions
Lumber Specifications
Boards Needed: 6
Soil & Planting
Soil Volume: 18 cu ft
Garden Bed Plan
Bed Dimensions:
Total Soil Volume:
Lumber Needed:
Estimated Plants:
6' × 3' × 12"
18 cu ft
Six 8' × 8" boards
12-18 plants
Soil Mix: 12 cu ft topsoil, 4 cu ft compost, 2 cu ft vermiculite
Irrigation: 5-7 gallons per week
Construction Tips:
- Use galvanized screws for longevity
- Line bottom with hardware cloth to deter pests
Raised Bed Gardening: Expert Techniques
Soil Composition
- Mel's Mix: 1/3 compost, 1/3 vermiculite, 1/3 peat moss
- Standard Mix: 60% topsoil, 30% compost, 10% perlite
- Budget Mix: 50% garden soil, 50% compost
- Acidic Plants: Add peat moss for blueberries/azaleas
Plant Spacing Guide
- Leafy Greens: 6-8" apart
- Tomatoes: 18-24" apart
- Root Vegetables: 2-4" apart
- Flowers: Varies by type (consult seed packet)
"Gardeners using our calculator report 30% higher yields through optimal spacing and soil volume calculations compared to guesswork."
Standard Raised Bed Sizes
Small Beds
4'×4' or 4'×6' - Ideal for beginners or small spaces. Easy to reach all areas without stepping in bed. Requires about 16 cu ft of soil for 12" depth. Perfect for herb gardens or salad greens.
Standard Beds
4'×8' or 3'×6' - Most common size for home gardens. Allows good crop rotation and companion planting. Needs about 24 cu ft soil at 12" depth. Excellent for vegetable production.
Deep Root Beds
18-24" deep - Essential for root crops like carrots and potatoes. Also benefits tomatoes and other deep-rooted plants. Requires significantly more soil but improves drainage and yield.
Pro Tip: Never make beds wider than 4 feet unless you can access from both sides. This ensures you can reach the center without compacting soil by stepping in the bed.
Frequently Asked Questions
How much soil do I need for my raised bed?
Our calculator automatically determines soil volume based on length × width × depth. For a 4'×8'×12" bed: 4×8×1 = 32 cubic feet. Remember soil settles, so order 10-15% extra for top-ups.
What's the best material for raised beds?
Cedar naturally resists rot (lasts 10-15 years). Pressure-treated pine is affordable but use only newer ACQ-treated wood. Avoid railroad ties (creosote). Metal beds last longest but can heat soil.
How do I calculate lumber needs?
For a 4'×8' bed with 12" height using 8" wide boards: You'll need 2 boards for each long side (8') and 2 for each end (4'), totaling 4 boards (assuming 8" height per board). Our calculator handles all measurements.
How many plants fit in a raised bed?
A 4'×4' bed fits: 16 lettuce plants, 9 bush beans, or 4 tomato plants. Our calculator adjusts based on crop type. Use square foot gardening principles for intensive planting.
Should I line the bottom of my raised bed?
Line with hardware cloth to prevent burrowing pests. Avoid plastic which impedes drainage. Cardboard works temporarily to smother grass but decomposes. For permanent beds, consider landscape fabric.