Soil Amendment Calculator
Estimate compost or amendment to top-dress a bed or lawn. Enter the area in square feet and the layer depth in inches to see cubic feet, yards and bags.
How to estimate soil amendment
- Enter the area you are covering in square feet.
- Enter how deep a layer you want to spread, in inches.
- Read off the cubic feet, cubic yards and bag count.
Examples
100 sq ft at 2 inches deep
Area 100, depth 2 in
16.6667 cu ft, 0.6173 cu yd, 9 bags at 2 cu ft
Frequently asked questions
How deep should a compost top dressing be?
A quarter to a half inch is plenty for an annual lawn top dressing. Garden beds can take one to three inches of compost worked into the surface before planting.
How many cubic feet are in a cubic yard?
There are 27 cubic feet in a cubic yard. Bulk compost is usually sold by the cubic yard, so the calculator converts your cubic feet for ordering in bulk.
Compost, manure or topsoil, which should I add?
Compost improves structure and feeds soil life and suits most beds. Aged manure adds nutrients, while topsoil adds bulk. Many gardeners blend compost with topsoil.
Should I mix it in or leave it on top?
For lawns, leave a thin layer on top and let it settle in. For beds, lightly work the amendment into the top few inches so roots reach it quickly.
Why round bags up?
Amendment is sold by the whole bag, so partial needs round up. A little extra is handy for topping up thin areas or for nearby pots and planters.
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