Garden Soil Mix Calculator
Calculate garden-bed soil volume and split the order into topsoil, compost and aeration components using adjustable mix shares.
Default project preview
1.96 yd³
Topsoil
0.98 yd³
Compost
0.59 yd³
Aeration material
0.39 yd³
Base volume
1.78 yd³
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Bed length
Enter this project assumption in ft. The current imperial default is 12 ft.
Bed width
Enter this project assumption in ft. The current imperial default is 4 ft.
Mix depth
Enter this project assumption in in. The current imperial default is 12 in.
Settlement allowance
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 50.
Topsoil share
Enter this project assumption in parts. The current imperial default is 50 parts. Minimum: 0.
Compost share
Enter this project assumption in parts. The current imperial default is 30 parts. Minimum: 0.
Aeration share
Enter this project assumption in parts. The current imperial default is 20 parts. Minimum: 0.
Topsoil bulk price
Enter this project assumption in per yd³. The current imperial default is 40 per yd³. Minimum: 0.
Compost bulk price
Enter this project assumption in per yd³. The current imperial default is 65 per yd³. Minimum: 0.
Aeration bulk price
Enter this project assumption in per yd³. The current imperial default is 80 per yd³. Minimum: 0.
How to read the outputs
Topsoil
50% of mix. Default preview: 0.98 yd³.
Compost
30% of mix. Default preview: 0.59 yd³.
Aeration material
20% of mix. Default preview: 0.39 yd³.
Base volume
before allowance. Default preview: 1.78 yd³.
Bed area
rectangular footprint. Default preview: 48 ft².
Bulk mix cost
component prices combined. Default preview: $108.53.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Bed volume = length × width × depth × settlement factor. Each component volume equals total order volume × its share ÷ the sum of all entered shares.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: July 30, 2026
Use this calculator to divide a target soil volume among topsoil, compost and drainage or aeration components using editable mix percentages. It supports purchasing and does not prescribe a universal planting mix.
Calculation steps
- 1Calculate the total filled volume.
- 2Confirm component percentages total 100%.
- 3Multiply total volume by each component fraction.
- 4Convert each component to supplier units and round separately.
Worked numerical example
A raised area requiring 3 yd³ with a 60/30/10 mix needs 1.8 yd³ topsoil, 0.9 yd³ compost and 0.3 yd³ aeration material before package rounding.
Purchasing and rounding
Bulk materials are rounded to delivery increments; bagged products are rounded to whole bags. Different components may use different sold units.
Interpret the result
The largest component controls most of the delivery volume, while small percentages can still require a full bag or bulk increment.
Page-specific assumptions
- Percentages are volume-based.
- Materials are measured loose.
- Settling allowance is included if needed.
- The selected mix is suitable for the plants and drainage.
Common mistakes
- Using weight percentages with volume quantities.
- Allowing percentages not to total 100%.
- Ignoring settling.
- Assuming one mix suits every planting.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
FAQ
Garden Soil Mix Calculator questions
Do the mix shares need to total 100?+
No. The calculator treats them as relative parts and normalizes them automatically.
Why add a settlement allowance?+
Loose soil and compost settle after filling and watering, so an allowance can help maintain the planned finished depth.
Is one mix suitable for every plant?+
No. Drainage, nutrient needs, native soil and crop type should guide the final recipe.