Planter Soil Volume and Bag Calculator
Estimate loose potting-medium volume and whole bags for round, tapered-round or rectangular containers with excluded and reused volumes.
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Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Calculate the geometric region between excluded lower depth and planned fill height, subtract the entered occupied/reused volume, then scale for the entered loose-volume reduction. Round the total requirement up to whole bags.
New filled volume=(usable region−occupied/reused volume)×count; loose volume=new filled volume/(1−reduction)
Worked example
Three cylindrical containers of 30 cm internal diameter filled from 3 to 25 cm use about 46.653 L of new filled medium. With an entered 10% loose-volume reduction, buy about 51.836 L: three 20 L bags.
Assumptions and input details
Use internal dimensions. Tapered sides vary linearly over the full container height; the radii at both fill boundaries are computed before taking the frustum volume. Excluded lower depth is a volume deduction, not advice to add a drainage layer. Occupied volume does not verify root-ball shape or fit. Reduction is entered, not a universal material property. Plant health, mixture selection and structural loading are outside this geometric shopping estimate.
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Choose from 23 length definitions, including explicitly labelled regional measures. Area conversions square the length factor; geometric volumes cube it.
The 36 volume definitions distinguish US liquid, US dry and Imperial measures. Cups carry an explicit definition. Japanese shō is 2401/1331 L and a gō is one tenth of it; the explicitly labelled 180 mL rice cup is separate.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · UK Imperial definitions · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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