How Much Soil to Fill a Raised Garden Bed: A Step-by-Step Guide for Vegetables

By Graham Fisher

Updated November 2026

To figure out how much soil to fill a raised garden bed, multiply the bed’s length, width and depth in feet, then divide by 27 to get cubic yards. That number tells you how much material to order or buy, and this guide walks you through measuring, choosing the right depth for your crops, and adding a little extra to allow for settling.

Step 1: Measure the Inside of Your Bed

Measure the inside dimensions, not the outside boards. A 4 × 8 foot bed made from 2-inch lumber has an interior of roughly 3.8 × 7.8 feet once you subtract the boards, and using the outer measurements will overestimate your soil needs. Measure in feet, and convert any inches to decimals (6 inches is 0.5 feet).

Shopping for one? See our guide: 5 Best Garden Soil in Bulks for Raised Beds and Gardens (2026).

Step 2: Choose the Right Soil Depth for Your Crops

Depth matters more than most beginners expect. Most vegetables do well in 6 to 12 inches of soil, but root crops and deep-rooted plants need more.

• 6 inches: Lettuce, spinach, radishes, herbs and other shallow-rooted greens.
• 8 to 10 inches: Peppers, bush beans, cabbage, kale and most general vegetables.
• 12 inches or more: Tomatoes, carrots, parsnips, winter squash and other deep-rooted crops.

If you plan to grow a mix, 10 to 12 inches covers nearly everything. For a deeper look at depth choices, see 7 Best Soil Depth Raised Garden Beds for Vegetables (2026).

Step 3: Calculate the Volume

Use this formula:

Length (ft) × Width (ft) × Depth (ft) = cubic feet

Then divide by 27 to convert to cubic yards, the unit most bulk suppliers sell by. For example, a 4 × 8 foot bed filled to 10 inches (0.83 feet) works out like this:

4 × 8 × 0.83 = 26.6 cubic feet, and 26.6 ÷ 27 = about 1 cubic yard.

If you want to skip the math, a dedicated Raised Garden Bed Soil Calculator: How Much Soil You Really Need will do it for you, though checking the numbers by hand is a good habit.

Step 4: Add Extra for Settling

New soil settles noticeably in the first few weeks, especially when it’s wet and loosely packed. Most gardeners add 10 to 15 percent to their total so the bed still looks full after the first watering. For a 1-cubic-yard calculation, order closer to 1.1 to 1.15 cubic yards.

Tools and Materials Checklist

1. Tape measure or yardstick
2. Calculator or phone app
3. Soil volume estimate with a 10 to 15 percent buffer
4. Wheelbarrow or tarp for mixing and moving soil
5. Rake and hand trowel for leveling

Quick Reference Table

Common Mistakes to Avoid

• Measuring the outside of the frame instead of the inside.
• Forgetting to convert inches to feet before multiplying.
• Skipping the settling buffer and finding the bed half-empty by midsummer.
• Filling deep beds entirely with bagged potting mix, which gets expensive fast. A layer of coarse fill at the bottom works well; see Raised Garden Bed Soil Layers: A Step-by-Step Guide for Vegetables.
• Ordering bulk soil without checking the delivered volume, since sellers sometimes use different units.

Recommended Gear

A good tape measure makes the first step far more accurate, especially on longer beds. Look for a sturdy steel-blade model that locks in place for measuring across the bed. View on Amazon

A garden wheelbarrow is useful for moving and mixing soil before spreading it. Choose one with a pneumatic tire if your yard is uneven. View on Amazon

FAQ

Can I fill a raised bed with just topsoil?

Topsoil alone often compacts and drains poorly in raised beds. Most gardeners blend it with compost and a bulking material such as perlite or coarse aged bark for better structure.

How deep should a raised bed be for tomatoes?

Aim for at least 12 inches, since tomato roots spread widely and benefit from deep, loose soil. Deeper beds also hold moisture more evenly during hot weather.

How often do I need to add more soil?

Plan to top up the bed by a few inches each year or two, because the soil level drops as organic matter breaks down and settles. Adding compost each season helps maintain the volume.

Conclusion

To work out how much soil to fill a raised garden bed, measure the interior, choose a depth that suits your crops, and convert the volume to cubic yards. Add about 10 to 15 percent for settling, and you’ll have a bed that’s full and ready to plant.

About Graham Fisher

Graham Fisher is part of our editorial team and reviews and edits our vegetable & edible gardening guides, checking product details against manufacturer specifications and owner feedback.