Calculator

Soil Calculator

Fill soil and amended garden-bed soil aren't interchangeable, and they don't weigh (or cost) the same per cubic yard — fill dirt is dense, compacted, and cheap, meant to raise grade or backfill; a bagged or bulk 'garden soil' or raised-bed mix is blended with compost and other lightweight organic matter to stay loose and well-drained for root growth. Using fill dirt in a raised bed compacts over a season and drains poorly; using an expensive amended mix just to level a low spot in the yard is an unnecessary cost.

This calculator sizes cubic yards needed for either use case from your bed or fill-area dimensions, since the volume math is the same but the material choice genuinely isn't.

Calculate your quantity

Bed area (sq ft)

Depth (in)

Bag size

cu ft per bag

Soil (bulk)

0.93 cu yd

Soil (bagged)

17 1.5 cu ft bags

Volume: 25 cu ft

Shopping summary

• 17 bag(s) of soil, or 0.93 cu yd bulk

This is an estimate — confirm structural work with a professional.

How this calculation works

Cubic yards = (area in sq ft x depth in inches / 12) / 27, same core formula as mulch and gravel. For a raised bed, use the bed's actual interior dimensions and full depth; for grade-fill, use the low-spot area and the depth needed to bring it level, which is often uneven across the area and best estimated from an average depth across a few measured spots.

Bulk densities differ by material: fill dirt is denser and heavier per cubic yard than an amended garden soil mix, which is blended lighter on purpose. This matters for delivery weight limits and for how much the soil will settle over the following weeks — amended mixes settle more (5-10% volume loss is normal) as organic matter breaks down, so a slight overfill on a new raised bed is expected, not a measuring error.

Common mistakes

Using cheap fill dirt in a raised bed intended for vegetables or flowers, which compacts and drains poorly compared to an amended mix.
Not accounting for settling — a freshly filled raised bed typically loses 5-10% of its volume within the first month as the mix settles, which isn't a sign anything went wrong.
Estimating grade-fill depth from a single measurement on an uneven low spot, understating the true volume needed.
Confusing topsoil with compost or garden-bed mix — topsoil alone is usually too dense and nutrient-poor for a productive raised bed without amendment.
Filling a raised bed completely with purchased mix top to bottom on a deep bed, when a cheaper base-fill layer (like coarse organic debris or fill dirt in the bottom third) under an amended top layer can meaningfully cut cost on beds deeper than about 18 inches, since roots for most vegetables don't need the full depth to be premium mix.
Not checking bulk soil for contamination history if sourced from an unknown pile or construction site — this matters especially for a food-growing bed.

Shopping summary

For raised beds, order an amended garden soil/raised-bed mix by the cubic yard (bulk) or bag, sized to interior bed volume plus a 5-10% settling allowance; for grade-fill, order plain fill dirt or topsoil by the cubic yard sized to the average fill depth across the low area.

Worked example: a raised bed 4x8 feet and 12 inches deep has an interior volume of 4 x 8 x 1 = 32 cubic feet, or about 1.19 cubic yards. Adding a 7% settling allowance brings the order to roughly 1.27 cubic yards — round up to 1.5 cubic yards bulk, or about 34 standard 1 cubic foot bags if buying bagged mix instead.

FAQ

How much will my raised bed soil settle?

Expect roughly 5-10% volume loss in the first month as organic matter in the mix breaks down and compacts — filling slightly above the bed's rim initially accounts for this.

Can I mix my own raised-bed soil instead of buying a pre-blended mix?

Yes — a common DIY blend is roughly equal parts topsoil, compost, and a coarse aggregate like perlite or coarse sand for drainage, though a quality pre-blended mix is often more consistent for a first-time bed.

Is bagged or bulk soil cheaper for a raised bed?

For a single small bed, bagged soil is often more convenient and comparably priced once you account for a bulk supplier's delivery minimum; for several beds or a large bed totaling more than roughly 2-3 cubic yards, bulk delivery is typically the better value per cubic foot, similar to the bag-vs-bulk crossover on mulch.

How much does a standard bag of garden soil weigh, and how many cubic feet does it hold?

Most bagged garden soil and raised-bed mix comes in 1-1.5 cubic foot bags, weighing roughly 30-40 lbs depending on moisture content — always check the bag's printed volume rather than assuming a flat cubic-foot figure, since bag sizing varies more between brands for soil than it does for concrete mix.