One measured bed · separate material orders
Raised Bed Soil Blend Calculator with Mulch Cap
Enter the blend parts you have chosen. The calculator splits measured fill among those components, rounds each package count separately, and keeps an optional mulch cap as its own order.
Calculation method
Split the measured fill, then price each package line
For each rectangular bed, the fill volume is its inside length × inside width × the fill depth-to-add. The total is divided in proportion to the parts you enter. Each component then uses its own label volume and optional price. A mulch cap is calculated from the same footprint with a separate depth.
US fill: square feet × depth in inches ÷ 12 = cubic feet
Metric fill: square metres × depth in centimetres ÷ 100 = cubic metres
Component share: total fill × component parts ÷ sum of all parts
Packages: component volume ÷ label volume, rounded up separately
The Iowa State University Extension mulch example uses measured area and entered depth to determine volume, then rounds according to the package quantity. NIST conversion tables provide the unit factors used for feet/inches, metres/centimetres, cubic feet/cubic yards and cubic metres/litres. This calculator applies those arithmetic steps to your inputs; it does not choose a soil recipe or layer depth.
Worked arithmetic
Example: one 4 × 8 ft bed
The measured footprint is 32 ft². With sample inputs of 10 in fill and a 2:1 parts split, the total is 32 × 10 ÷ 12 = 26.67 ft³. The two shares are 26.67 × 2 ÷ 3 = 17.78 ft³ and 26.67 × 1 ÷ 3 = 8.89 ft³. At 1.5 ft³ per bag, those volumes round separately to 12 and 6 bags.
A separate sample 2 in cap gives 32 × 2 ÷ 12 = 5.33 ft³. At 2 ft³ per bag, that rounds to 3 bags. These inputs demonstrate the arithmetic only; the page does not recommend a ratio, depth or package size.
Common questions
Raised bed soil blend and mulch FAQ
How does a raised-bed soil blend calculator split the fill?
Measure each bed and enter the fill depth you plan to add. Enter the number of parts for each component; the calculator divides total fill volume in proportion to those parts and rounds each component up using its own package size.
Does this page recommend a soil recipe or blend ratio?
No. You enter the component names and parts for a blend you have already chosen. The calculator does not recommend ingredients, a ratio, soil type or planting practice.
Can beds use different blend ratios in one estimate?
The entered parts apply to all beds in one estimate. Run a separate estimate for beds that use a different blend ratio.
Can I add mulch over the soil blend?
Yes. Enter a separate mulch depth-to-add and package volume. The mulch volume and whole-package quantity are calculated independently from the soil fill.
How are partial packages handled?
Each component volume is divided by that component's package volume, and the result is rounded up to a whole package. The mulch cap uses its own package volume and rounding.
Can I use metric measurements and prices?
Yes. Switch between feet and inches or metres and centimetres. Enter package volume in cubic feet for US units or litres for metric units. Optional prices are multiplied by each rounded package count; use the same currency for all entered prices.