What soil mix works best in raised beds?

A balanced raised bed mix often combines quality topsoil, compost, and a light material such as coco coir, peat moss, perlite, or vermiculite. The best blend depends on what you plan to grow.

How deep should soil be in a raised bed?

Leafy greens can grow in 6 to 8 inches, many vegetables prefer 10 to 12 inches, and deep-rooted crops such as tomatoes or carrots do better with 18 inches or more.

Do raised beds need drainage space?

Raised beds need a way for water to leave the root zone. Use open bottoms where possible, and only add a drainage layer when the bed sits on hard paving or a sealed base.

Raised Bed Soil Calculator

Calculate the exact amount of soil needed for your raised beds. Supports multiple shapes, custom soil mixes, and includes weight calculations for rooftop gardens.

Raised Bed Calculator

Units

Settling Allowance

Your Raised Beds

Bed Shape

Length (ft)

Width (ft)

Depth (inches)

Include drainage layer (gravel/rocks)

Soil Mix

Mel's Mix (Square Foot Gardening)Premium mix for maximum productivityBest for: All vegetables, intensive plantingBudget Vegetable MixCost-effective mix for vegetablesBest for: General vegetable gardeningPremium Organic MixRich organic blend for optimal growthBest for: Organic vegetables and herbsFlower & Perennial MixWell-draining mix for ornamentalsBest for: Flowers and perennial plantsHerb Garden MixFast-draining mix for Mediterranean herbsBest for: Herbs, especially Mediterranean varietiesCustom MixCreate your own blendBest for: Customized to your needs

Peat Moss Alternative

Aeration Material

Advanced Options

Include Hugelkultur base (wood logs/branches for deep beds)

Show accessibility recommendations

Pricing Information

Bulk Price ($ per cubic yard)

Bagged prices are used for comparison only. Adjust if needed for your area.

Plant Depth Requirements Guide

Shallow Root Vegetables (6-8 inches)

Lettuce6"-8"

Spinach6"-8"

Radishes6"-8"

Green Onions6"-8"

Herbs (most)6"-8"

Medium Root Vegetables (12 inches)

Bush Beans8"-12"

Beets10"-12"

Broccoli12"-12"

Cabbage12"-12"

Cauliflower12"-12"

Chard8"-12"

Kale8"-12"

Peas8"-12"

Peppers12"-12"

Strawberries8"-12"

Deep Root Vegetables (18-24 inches)

Tomatoes18"-24"

Carrots12"-18"

Eggplant18"-24"

Parsnips18"-24"

Potatoes18"-24"

Sweet Potatoes18"-24"

Squash18"-24"

Cucumbers12"-18"

Melons18"-24"

Asparagus24"-36"

Perennials & Small Shrubs (24+ inches)

Blueberries24"-36"

Raspberries24"-36"

Dwarf Fruit Trees36"-48"

Roses24"-36"

Perennial Flowers18"-24"

Complete Guide to Raised Bed Soil

Understanding Soil Mixes

Mel's Mix (Square Foot Gardening)

The gold standard for intensive vegetable gardening, created by Mel Bartholomew. This mix provides excellent drainage, moisture retention, and nutrients:

1/3 Peat Moss or Coir: Retains moisture while providing good drainage
1/3 Vermiculite: Improves aeration and holds nutrients
1/3 Blended Compost: Provides nutrients from multiple sources

Budget-Friendly Alternatives

While Mel's Mix is excellent, it can be expensive for large beds. Consider these alternatives:

60/30/10 Mix: 60% topsoil, 30% compost, 10% perlite or sand
50/50 Mix: Equal parts topsoil and compost for basic gardens
Lasagna Method: Layer cardboard, straw, leaves, and compost

Sustainable Alternatives

Peat Moss vs. Coconut Coir

Peat Moss: Excellent water retention but non-renewable resource
Coconut Coir: Sustainable alternative, similar properties, slightly higher pH

Vermiculite vs. Perlite

Vermiculite: Better water retention, holds nutrients, more expensive
Perlite: Better drainage, lighter weight, less expensive

Cost-Saving Strategies

Hugelkultur Method

For deep beds (18+ inches), place logs, branches, and wood debris in the bottom third. This reduces soil needs by 30-40% and provides long-term nutrients as wood decomposes.

Bulk Buying Tips

Order with neighbors to meet minimum delivery requirements
Buy in spring when demand is lower
Consider "garden blend" mixes from local suppliers
Check with municipal composting programs

Filling Strategy

Layering for Deep Beds

Bottom 4-6": Drainage layer (gravel or coarse wood chips)
Next 6-12": Hugelkultur layer (logs, branches) or core materials
Top 12-18": Premium soil mix for root zone

Settling Considerations

Fresh compost settles 15-20% in first year
Peat moss settles 10-15% when first wetted
Always overfill beds initially
Top up with compost annually

Special Considerations

Rooftop and Balcony Gardens

Weight limits: Most roofs support 15-20 lbs/sq ft
Use lightweight mix: More perlite, less topsoil
Drainage is critical: Include drainage layer and overflow holes
Consider modular systems: Distribute weight evenly

Contaminated Soil Areas

Line bed bottom with landscape fabric
Use imported soil only
Consider deeper beds (24+ inches)
Test soil for heavy metals if concerned

Maintenance

Annual Top-Up

Add 2-3 inches of compost each spring
Mix gently into top 6 inches
Replace mulch layer
Test soil every 2-3 years

Signs of Soil Problems

Poor drainage: Water pools on surface
Compaction: Hard surface, poor root penetration
Nutrient depletion: Pale plants, poor growth
pH imbalance: Specific nutrient deficiencies

Garden questions, answered

Common questions before you buy materials

Use these quick answers alongside the calculator so you can plan the right amount, avoid waste, and keep your garden project moving.

What soil mix works best in raised beds?: A balanced raised bed mix often combines quality topsoil, compost, and a light material such as coco coir, peat moss, perlite, or vermiculite. The best blend depends on what you plan to grow.
How deep should soil be in a raised bed?: Leafy greens can grow in 6 to 8 inches, many vegetables prefer 10 to 12 inches, and deep-rooted crops such as tomatoes or carrots do better with 18 inches or more.
Do raised beds need drainage space?: Raised beds need a way for water to leave the root zone. Use open bottoms where possible, and only add a drainage layer when the bed sits on hard paving or a sealed base.