🪴 Garden Bed Soil Mix Calculator

1Choose Your Bed Shape and Measure It

Select whether your bed is rectangular (or square) or circular, then enter its dimensions. For rectangular beds, measure the length and width in feet and the depth in inches. For round beds, measure the diameter across the widest point in feet and the depth in inches. The calculator converts everything internally and handles the circle math for you.

Measure the actual fill depth you intend to use, not the full height of the bed walls. Most vegetables thrive in 10 to 12 inches of soil, while shallow-rooted greens and herbs are happy in 6 to 8 inches. Deeper beds need more mix but reduce watering frequency and give roots room to escape summer heat.

2Pick the Right Soil Recipe

Select the mix recipe that suits your project. The Standard Mix is a balanced all-purpose blend for in-ground raised beds. Mel's Mix is the light, peat-and-vermiculite-style blend favored for square-foot gardening. The Lasagna recipe leans on topsoil and compost for sheet-mulched beds, the Container Mix is the lightest and most free-draining, and the Native Blend keeps a majority of local soil for low-maintenance plantings.

Each recipe sets the percentage of topsoil, compost, and the peat or coir component, and the calculator translates those percentages into exact volumes and bag counts. If you are unsure, the Standard Mix is a safe, productive starting point for the great majority of edible and ornamental beds.

3Tell the Calculator What You're Growing

Choose the plant type that best matches your bed: vegetables, flowers, herbs, acid-loving plants, succulents, or native species. This selection drives the target pH range and the amendment advice, because different plants thrive in different soil chemistry. Blueberries and azaleas demand acidic soil, while most herbs prefer it slightly alkaline.

Matching soil chemistry to the crop pays off all season. A bed tuned to the right pH lets plants take up nutrients efficiently, reducing the need for extra fertilizer and preventing the nutrient lockout that causes yellow leaves and stunted growth even when feeding is generous.

4Review Volumes and the Shopping List

The results show your total volume in cubic feet, cubic yards, and quarts, plus an estimated cost. The component table breaks the recipe into individual ingredients and tells you how many one-cubic-foot and two-cubic-foot bags of each to buy, so you can shop without doing arithmetic in the store aisle.

Use the cubic-yard figure to decide between bagged and bulk soil: beds approaching or exceeding a cubic yard are almost always cheaper to fill from a bulk delivery. Whichever route you choose, the per-component breakdown ensures you bring home the correct proportions of topsoil, compost, and aeration material.

5Mix, Fill, and Plan for Settling

Combine your components thoroughly before or as you fill the bed, rather than layering them, so roots encounter a consistent blend at every depth. Moisten the mix as you go to help it knit together and to reveal any dry pockets that need more water.

Add roughly ten percent extra volume to account for settling, which is most pronounced in compost-rich mixes during the first few weeks. Plan to top-dress with fresh compost each season to replace what breaks down, keeping the bed full and the soil biology active year after year.

💰 Stop Wasting Money on Soil

Buying soil by guesswork almost always means surplus bags left to harden in the shed or, worse, a half-finished bed and a second trip to the garden center. Calculating the exact volume up front lets you order the right amount once, compare bagged versus bulk pricing, and keep your project on budget.

🌿 Healthier, More Productive Plants

The right blend of topsoil, compost, and aeration material gives roots the balance of moisture, oxygen, and nutrients they need. Plants grown in a well-structured, correctly amended mix establish faster, resist disease better, and reward you with stronger growth and bigger harvests.

💧 Better Drainage and Water Retention

Matching the recipe to your bed and plants strikes the balance between holding moisture and shedding excess water. That means fewer waterlogged roots, less drought stress between waterings, and a garden that copes far better with both heavy rain and dry spells.

⚗️ Correct pH for What You Grow

Even a perfect physical mix underperforms if the chemistry is wrong. By suggesting a target pH for vegetables, acid-lovers, succulents, and more, the calculator helps you create soil where nutrients are actually available to the plants you have chosen.

📋 A Clear Shopping List

The component breakdown converts percentages into the exact number of one- and two-cubic-foot bags of each ingredient. You walk into the store knowing precisely what to grab, with no mental arithmetic and no risk of coming home with the wrong proportions.

🌍 More Sustainable Choices

Knowing your real volumes makes it practical to choose renewable coir over mined peat, to source compost locally, and to avoid the waste of over-ordering. Building soil thoughtfully reduces your garden's footprint while improving long-term fertility.