Raised-bed soil calculator
Work out how much soil/compost mix you need to fill a raised bed, or — if you already have a set amount of mix — how deep it will fill a given footprint.
Result
Soil mix required
Soil mix required
Result
Fillable height
How to use this tool
- Measure the internal length, width and height of the raised bed.
- Read the volume of soil mix required, or use reverse mode if you already have a fixed amount of mix.
Assumptions
- Assumes a simple rectangular bed with vertical sides — an irregular shape needs a rough equivalent rectangle.
- The result is geometric bed volume, not a prescribed recipe. Choose a suitable raised-bed growing medium for the plants; topsoil/compost proportions are optional, context-dependent guidance.
Technical details: what the fields mean
- Length
length - Internal length of the raised bed.
- Width
width - Internal width of the raised bed.
- Height
height - Internal height (depth) of the raised bed, from the base to the top of the sides.
Methodology
Volume = length × width × height — a straightforward rectangular-box calculation.
Worked example
1.2m × 0.9m bed, 0.3m deep
Inputs: Length: 1.2 m, Width: 0.9 m, Height: 0.3 m
Result: 0.32 m³ (324 L) of soil mix required
Practical guidance
- Choose a raised-bed mix for the intended plants and local conditions. A topsoil surface layer, compost amendment and full bed fill are different quantities and uses.
- The calculator reports the entered internal dimensions as volume; account for headroom or settling only if it matches your plan.
Common mistakes
- Confusing a raised bed's full fill volume with a topsoil surface-layer or compost-mulching quantity.
- Assuming one soil/compost recipe suits every bed, crop, climate or purchased product.
FAQs
How much raised-bed mix do I need for a 1.2m x 0.9m bed?
At 0.3m internal fill depth, the rectangular volume is 0.324m³ (324L). This is total geometric volume, not a recommendation for a particular mix or a topsoil surface layer.
I already have some soil mix — how deep will it fill my bed?
Use reverse mode below: enter your available volume plus the bed's length and width to see the depth it will fill.
Last reviewed: 2026-10-11
A simple rectangular-volume estimate — doesn't account for tapered or irregular bed shapes.
This tool provides an indicative estimate, based on the assumptions stated above.
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