Soil Calculator - Topsoil Volume and Bag Count for Garden Beds

Garden soil calculator - volume, bags and cost in one step

Enter the area you need to fill, pick the layer depth and soil type. The calculator returns the exact volume in cubic meters and liters, the number of bags (50L or 80L depending on type) and a cost estimate. A 10 m2 vegetable bed at 20 cm depth needs 2,000 liters - that is 25 bags of 80L topsoil. But the same bed at only 10 cm needs just 13 bags. Getting the depth right saves money and trips to the store.

The problem - and how this calculator solves it

THE PROBLEM

You eyeball the bed and buy 10 bags.

Halfway through, the bags run out.

Second trip: another 8 bags, another $50.

After watering, the soil settles 25%.

Total wasted: $50 + 2 hours + uneven bed

THE SOLUTION

Measure the area: 10 m2.

Pick depth: 15 cm (raised bed).

Calculator: 19 bags of 80L.

Add 15% for settling: 22 bags.

One trip, correct amount, level bed

How to use the soil calculator - step by step

Area (m2) - measure length x width of the bed, border or lawn section. For irregular shapes, break into rectangles and add them up.
Layer depth - lawn top-up 5 cm, flower bed 10-15 cm, vegetable bed 20-30 cm. Deeper layers settle more, so the calculator warns you to add 10-20% extra.
Soil type - topsoil (general purpose, 80L bags), peat (acid-loving plants, 80L), compost (soil amendment, 50L), universal mix (containers, 50L). Each has a different bag size and price.
Price per bag (optional) - enter your local price for a cost estimate. Without it, the calculator uses average US retail prices.
Read the results - volume in m3 and liters, exact bag count, and total cost.

Layer depth reference

Use case	Depth	80L bags per 10 m2	Best soil type
Lawn levelling	5 cm	~7	Topsoil
Flower bed	10-15 cm	13-19	Topsoil or universal
Vegetable bed	20-30 cm	25-38	Topsoil + compost mix
New lawn	10 cm	~13	Topsoil
Blueberry / azalea bed	15-20 cm	19-25	Peat (pH 3.5-4.5)

Soil type comparison - price, bag size and best use

Soil type	Bag size	Price range	Best for
Topsoil / garden soil	80 L	$5-8	Beds, borders, lawn repair
Peat / acidic substrate	80 L	$8-12	Blueberries, azaleas, rhododendrons
Compost	50 L	$4-7	Soil amendment, organic fertilising
Universal potting mix	50 L	$3-5	Containers, hanging baskets, general fill
Bulk delivery (dump truck)	1,000+ L	$30-50/m3	Large beds, new lawns (3+ m3)

Practical examples

Small vegetable bed (2 x 3 m, 20 cm deep): 6 m2 x 0.2 m = 1,200 L = 15 bags of 80L topsoil. Add 20% for settling = 18 bags. Cost at $6/bag: $108.

Flower border (4 x 2.5 m, 10 cm deep): 10 m2 x 0.1 m = 1,000 L = 13 bags of 80L. With settling: 15 bags. Cost at $6/bag: $90.

Lawn top-up (50 m2, 5 cm): 50 x 0.05 = 2,500 L = 32 bags of 80L. At $6/bag: $192. Bulk delivery (2.5 m3 at $40/m3 + $80 delivery): $180 - cheaper and faster.

Raised bed (1.2 x 0.6 x 0.4 m): 0.72 m2 x 0.4 m = 288 L. Mix: 60% topsoil + 20% compost + 20% perlite. Need 4 bags of 80L topsoil + 2 bags of 50L compost.

Blueberry bed (3 x 1.5 m, 20 cm peat): 4.5 m2 x 0.2 m = 900 L = 12 bags of 80L peat. At $9/bag: $108. Add sulphur chips to maintain pH 4.0-5.0.

FAQ

How many bags of soil do I need for 10 m2?

It depends on depth. At 5 cm: 7 bags of 80L. At 10 cm: 13 bags. At 20 cm: 25 bags. Always add 10-20% extra because bagged soil settles after watering.

Bags vs bulk delivery - when does bulk make sense?

Bags cost roughly $75/m3. Bulk topsoil runs $30-50/m3 plus $80-120 delivery. Break-even point: around 3 m3 (about 38 bags). Below that, bags are easier. Above that, a dump truck saves money and time.

Why does soil settle after spreading?

Bagged soil is fluffed up during packaging. After spreading and the first rain or watering, air pockets collapse and the layer drops by 20-30%. A 10 cm layer becomes 7-8 cm. Plan for this by adding 2-3 cm extra depth.

Can I mix different soil types?

Yes, and it is often the best approach. A popular recipe for vegetable beds: 60% topsoil + 20% compost + 20% perlite or coarse sand. This gives nutrients, organic matter and drainage. Avoid mixing peat with clay - it creates a waterlogged layer.

What is the difference between topsoil and compost?

Topsoil is mineral-based soil with some organic content - it provides structure and bulk. Compost is fully decomposed organic matter - it provides nutrients and improves water retention. Use topsoil as the main fill and compost as a 20-30% amendment.

How do I know if my soil is good quality?

Good topsoil is dark brown, crumbles when squeezed (not sticky clay, not pure sand), smells earthy (not sour), and has visible organic matter. Avoid soil with stones, roots, or construction debris. A simple squeeze test: form a ball, then poke it - good loam crumbles, clay stays solid, sand falls apart.

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