Compost and topsoil calculator

Our Compost and Topsoil Calculator can help you determine the compost or topsoil needs for site development projects. This includes completing the permitting application for meeting the post-construction soil standard.

Use it to calculate:

• A custom compost amendment rate, which is the number of inches of compost to be layered over the site surface and mixed in
• Quantity of compost needed in cubic yards
• Quantity of site soil to be stockpiled in cubic yards
• Quantity of imported topsoil needed in cubic yards

STEP 1

Visit the King County Post-Construction Soil Standard page to understand code requirements and soil management options.

STEP 2

Determine which soil management option(s) are needed for each area marked on your project site map.

STEP 3

For soil treatment options that involve adding compost to the soil, you need to choose either the pre-approved amendment rate of application or a custom amendment rate. A custom amendment rate will be lower than the pre-approved rate for most sites. To calculate a custom amendment rate, you will need to enter information from laboratory tests* of the site soil and specified compost products.