What is Soil/Mulch Calculator?

The Soil/Mulch Calculator determines how many bags or cubic yards of soil, mulch, or compost you need for your garden beds, raised planters, or landscaping projects. Enter your area dimensions and desired depth to get precise material quantities.

Pick from rectangular, circular, tree-ring, or triangular beds, add as many separate areas as you have for one combined order, and work in metric (m, cm, litres) or imperial (ft, in, cubic feet) with the bag size you actually buy. The result shows bulk volume in cubic yards or cubic metres, an exact bag count rounded up so you don't end up two bags short on installation day, and an approximate weight for deciding between pickup and delivery.

How to use

1. Enter the length and width of your area (or radius for circular beds) and the desired fill depth.
2. Pick your material (topsoil, compost, bark, cedar or rubber mulch, pea gravel, river rock, and more), then choose the bag size you'll buy.
3. View the total volume needed in cubic feet/yards and the exact number of bags to purchase.

When to use

• Filling a new raised bed and need to know whether to buy bags or order bulk delivery.
• Topdressing a mulch ring around trees and want exactly enough for 2-inch depth.
• Estimating gravel for a circular fire-pit pad before driving to the landscape yard.

Result

Filling a 4×8 foot raised bed to 12 inches deep — the calculator shows 32 cubic feet needed, which is 16 bags of 2 cu ft topsoil or approximately 1.2 cubic yards for bulk delivery.

FAQ

How deep should I make the layer of mulch?

Two to three inches (5-8 cm) is standard for ornamental beds. Thicker mulch can smother roots and trap moisture against tree trunks. For gravel paths plan on 2-3 inches over a compacted base, and for topsoil in a new raised bed go 8-12 inches.

Why is the bag count higher than the cubic-feet number divided by bag size?

The calculator rounds up to whole bags because you can't buy a fraction of a bag at the store. It also assumes the listed bag volume is loose-fill; settling after watering can lose 10-20% of volume, so rounding up gives a small buffer.

Does this work for topsoil that's sold by weight instead of volume?

A 40-pound bag of topsoil is typically around 0.5 cubic feet, but it varies with moisture content. If the bag lists weight only, weigh one and divide by the soil's bulk density (about 75-100 lb per cubic foot for damp topsoil).

When is bulk delivery cheaper than bags?

Once you cross roughly 1 cubic yard (27 cubic feet, or 14 of the 2-cu-ft bags), bulk by-the-yard pricing usually beats bagged. Below that, delivery fees and minimum order quantities make bags simpler.

Does compost compress more than mulch when I water it in?

Yes. Fresh compost can lose 25-30% of its volume in the first month as organic matter breaks down and settles. Mulch and gravel hold their loft better. For new compost beds plan on topping up after a few weeks.

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