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Generated on: July 20, 2026 at 09:33 PM

Raised Bed Soil Calculator

Inputs

Bed length2.4 m
Bed width1.2 m
Fill depth30 cm
Number of beds1
Bag size50 l

This is an estimate based on the bed dimensions and a single fill depth. Actual needs vary with soil settling, the compaction of bagged products, and uneven ground. Bag volumes are nominal and can differ between brands. Buy a little extra to allow for settling and to top up after the first watering.

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Lifestyle

Raised Bed Soil Calculator

Estimate the soil volume needed to fill raised garden beds and the number of bags to buy from the bed dimensions, fill depth, and bag size.

Inputs

≥ 0 m
≥ 0 m
≥ 0.1 cm
1 – 100
≥ 0.1 l

Results

Enter a value to see results.

Details

Filling 1 bed(s) of 2.4 m × 1.2 m to a depth of 30 cm needs about ... of soil, or roughly ... bags of 50 l each.

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Raised Bed Soil

A raised bed is filled by buying enough soil to cover its footprint to a chosen depth, and the volume needed is the bed length times the width times the fill depth. This calculator converts that volume into the number of bagged soil products to buy, so a bed can be filled without running short or stacking up surplus bags.

Volume of a bed

The soil in one bed fills a rectangular box: its base is the bed footprint and its height is the fill depth. The volume of a single bed, and the total across several identical beds, is:

Vbed=l⋅w⋅dVtotal=Vbed⋅n\begin{aligned} V_{\text{bed}} &= l \cdot w \cdot d \\ V_{\text{total}} &= V_{\text{bed}} \cdot n \end{aligned}

where ll and ww are the bed length and width, dd is the fill depth, and nn is the number of beds. Bagged soil is sold in fixed volumes, so the number of bags is the total divided by the bag size, rounded up to the next whole bag:

N=⌈Vtotalb⌉\begin{aligned} N &= \left\lceil \frac{V_{\text{total}}}{b} \right\rceil \end{aligned}

where bb is the volume of one bag.

Worked example

Consider two beds, each 2.4 m long and 0.8 m wide, filled to a depth of 25 cm, using 40 L bags:

Vbed=2.4⋅0.8⋅0.25=0.48 m3Vtotal=0.48⋅2=0.96 m3=960 LN=⌈96040⌉=24 bags\begin{aligned} V_{\text{bed}} &= 2.4 \cdot 0.8 \cdot 0.25 = 0.48 \ \text{m}^3 \\ V_{\text{total}} &= 0.48 \cdot 2 = 0.96 \ \text{m}^3 = 960 \ \text{L} \\ N &= \left\lceil \frac{960}{40} \right\rceil = 24 \ \text{bags} \end{aligned}

The two beds need about 0.96 cubic metres of soil, or 24 bags of 40 litres each.

Consider two beds, each 8 ft long and 4 ft wide, filled to a depth of 12 in, using 2 cu ft bags:

Vbed=8⋅4⋅1=32 ft3Vtotal=32⋅2=64 ft3N=⌈642⌉=32 bags\begin{aligned} V_{\text{bed}} &= 8 \cdot 4 \cdot 1 = 32 \ \text{ft}^3 \\ V_{\text{total}} &= 32 \cdot 2 = 64 \ \text{ft}^3 \\ N &= \left\lceil \frac{64}{2} \right\rceil = 32 \ \text{bags} \end{aligned}

The two beds need about 64 cubic feet of soil, or 32 bags of 2 cubic feet each.

Choosing the depth

Most vegetables and flowers root well in 25 to 30 cm10 to 12 in of soil, while shallow-rooted herbs and salad greens manage with 15 to 20 cm6 to 8 in. A deeper bed needs proportionally more soil, so the depth is the input that most changes the bag count. Soil also settles after the first few waterings, so it is common to buy one or two extra bags per bed to top up.

For estimating the loose material spread on top of finished beds, see Mulch & Garden Soil Calculator.

Frequently Asked Questions (FAQ)

How much soil does a raised bed need?

The soil volume is the bed footprint multiplied by the fill depth. A 2.4 × 1.2 m bed filled to 30 cm holds about 0.864 cubic metres, which is roughly 864 litres or about 18 bags of 50 litres each. Multiply by the number of beds for the total.

The soil volume is the bed footprint multiplied by the fill depth. An 8 × 4 ft bed filled to 12 in holds about 32 cubic feet, which is roughly 16 bags of 2 cubic feet each. Multiply by the number of beds for the total.

What should I fill a raised bed with?

A common mix is roughly equal parts topsoil, compost, and an aeration material such as coarse sand or composted bark. Filling the lower portion of a deep bed with coarse organic material reduces the amount of bagged mix required, though the bed will settle more as that layer breaks down.

Why do raised beds need topping up each year?

Organic matter in the mix decomposes over a season, so the soil level drops by a few centimetres. Adding a layer of compost each year restores the depth and replaces nutrients. Plan for an extra one to two bags per bed annually to keep the fill level steady.

Disclaimer

This is an estimate based on the bed dimensions and a single fill depth. Actual needs vary with soil settling, the compaction of bagged products, and uneven ground. Bag volumes are nominal and can differ between brands. Buy a little extra to allow for settling and to top up after the first watering.

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