GardenKitHow it works
Mulch is calculated as a separate layer over the bed footprint; it is not subtracted from the soil fill estimate. Enter the intended depth of new mulch, accounting for any usable existing layer yourself. Use the label’s volume per bag and add an allowance only if needed. The model assumes the full rectangle is covered and does not subtract stems, paths or gaps around trunks. Choose a depth and material suitable for the plants and keep mulch away from sensitive stems according to local guidance.
Formula
Litres = length × width × mulch depth × 1000 × (1 + allowance/100). Bags = round up (litres ÷ bag volume).
Example
For a 3 × 1.2 m bed, a 5 cm mulch layer is 180 L. A 10% allowance raises this to 198 L. With 50 L bags, buy four bags, or 200 L total. At 8 per bag, the material estimate is 32. Purchased excess after rounding is measured against the allowance-inclusive requirement. A zero-depth layer needs zero bags.
Assumptions and limitations
Use product labels and local growing guidance. Defaults are examples. Assumptions use your inputs, not live weather or crop-specific prescriptions. Volume estimates exclude delivery and tax. Bag quantities round up.
Sources and assumptions
University of Minnesota Extension · Garden bed · University of Minnesota Extension · Water
Frequently asked questions
Are my garden measurements uploaded?
No. The tools save your current bed and settings in this browser. Clear this site’s data to remove them.
Does switching units change the result?
No. Dimensions stay in metres internally. Imperial views use feet and inches, cubic feet for bags and US gallons for water.
Are the defaults recommendations for my plants?
No. They are worked examples. Use product labels, crop requirements, soil moisture and local growing guidance.