Knowing how much soil or compost you need saves money and prevents shortages or leftover bags. This free Raised Bed & Compost Calculator helps you quickly calculate the exact volume of soil or compost required for any raised bed or garden area based on its dimensions and desired depth.
Raised Bed & Compost Calculator
Calculate how much soil or compost you need for your garden bed.
Standard bag size assumed: 1.5 or 2 cubic feet (common in most garden centers). Adjust according to the bags available in your area.
For new raised beds, a mix of 30% compost and 70% topsoil or garden soil is a popular and effective ratio. This provides good nutrients while maintaining proper structure and drainage.
Always order a little extra (about 10%) to account for settling after watering and natural compaction over time.
Frequently Asked Questions
How does the raised bed calculator work?
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It multiplies length × width × depth to get the total volume, then converts it into cubic feet or cubic meters. It also calculates how much of that volume should be compost based on the percentage you choose.
What depth should I use for a raised bed?
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Most vegetable raised beds work well with 10–12 inches of soil. Deeper beds (12–18 inches) are better for root crops like carrots and potatoes.
How much compost should I mix in?
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20–40% compost is ideal for most situations. 30% is a safe and widely recommended starting point for new raised beds.
Do I need to buy extra soil?
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Yes. Soil settles after watering. It is wise to buy about 10% more than the calculated amount to top up the bed after the first few waterings.
Can I use this for in-ground garden beds?
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Yes. Simply enter the length, width, and the depth of the amendment layer you want to add (for example 2–4 inches of compost).
Disclaimer: This calculator provides general volume estimates. Actual bag sizes and soil density can vary. Always check the volume printed on the bags available at your local garden center.