Biology
Work out how much compost you need for a bed or area, in cubic yards, cubic feet, litres and bags.
Your inputs
Change any value — everything updates instantly.
Longest side of the area.
Shorter side of the area.
1–3 inches worked into beds.
Same-size areas to fill.
Try an example
Compost needed
0.25 cubic yards
This means you need about 0.25 cubic yards — roughly 4 bags of 2 cubic feet each.
What you are seeing
The box shows your area, 10 × 4 ft.
It fills with compost to 2 inches deep.
That fill is 6.7 cubic feet in total.
Cubic feet
6.67 ft³
Volume in cubic feet.
Litres
189 L
Same volume in litres.
2 ft³ bags
4 bags
Rounded up to whole bags.
1.5 ft³ bags
5 bags
If you buy smaller bags.
Area covered
40 ft²
Total surface you are covering.
Result explanation: How much compost to buy
0.25 yd³ (0.19 m³).
Real-life comparison: Bags are usually easiest for small amounts like this.
Low, normal or high? Mix compost into the top few inches of soil.
Volume needed against depth
How to read this chart: Each extra inch adds the same amount. The red dot is your depth.
Multiplies area by depth to find how much compost fills the space.
0.25 cubic yards.
4 bags of 2 ft³.
Buy 5–10% extra for settling and uneven ground.
Inches ÷ 12 makes every length feet; ÷ 27 converts to cubic yards.
ft³ = length × width × (depth ÷ 12) × beds; yd³ = ft³ ÷ 27
Symbols
Why this formula works
A bed is a box; its volume is length × width × height.
Unit check
ft × ft × ft = ft³; 27 ft³ = 1 yd³ ✓
Worked example
Common mistakes
You need 0.25 cubic yards of compost.
A cube 3 ft on every side — 27 cubic feet, about 765 litres.
Yes, 5–10% extra covers settling and uneven ground.
Split the shape into rectangles and add them, or use the average length and width.
Loose soil and compost settle over weeks; you may need a top-up.
Reviewed 2026-09-25 · Next review 2027-09-25
Important limitation. Planning estimate. Supplier bag sizes and settling vary.
Tell us if a formula, unit, explanation, or result needs attention. Your message will include this calculator’s name and page.
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