This soil calculator turns a garden bed, planter or lawn-topdressing project into an order: the volume in cubic feet and cubic yards, and the bag count at the standard retail sizes, with a settling allowance so the bed is still full after the first watering. Soil is the material DIYers most consistently under-order — it compacts, it settles, and bags are smaller than they look — so the arithmetic here is deliberately conservative in your favor.

Volume –
With settling allowance –
Order –

Rule of thumb check: 1 cubic yard covers 324 sq ft at 1 inch deep, 108 sq ft at 3 inches, 27 sq ft at 12 inches. If your number disagrees wildly with that table, re-check the depth units — inches versus feet is the classic soil-ordering error.

Soil Math: Volume First, Bags Second

Every soil question is a volume question wearing a gardening costume. Length × width × depth gives cubic feet; 27 cubic feet make a cubic yard. Bags are sold by the cubic foot (0.75, 1, 1.5 and 2 cu ft are the common sizes), bulk soil by the cubic yard, and the conversion errors happen at that seam. Work the volume in cubic feet first — as this calculator does — then decide the packaging: under about 10 cu ft, bags are convenient; between 10 and 27 cu ft, compare bag totals against a half-yard bulk tote; over a yard, bulk delivery almost always wins on price and on trips.

Depth is the input people fudge. Raised beds are typically filled 10–12 inches for vegetables (roots want depth), 6–8 inches for flowers and herbs, and the “top up an existing bed” job is usually 2–3 inches of compost-rich mix rather than full soil. Topdressing a lawn takes ¼–½ inch. Amending a native garden bed before planting is typically worked out at 2–3 inches of compost over the area. Enter the honest depth — one phantom inch across a 4 × 8 bed is 2.7 cu ft, nearly two bags, in either direction.

Worked Example (Verified)

  • One 4 ft × 8 ft raised bed, 12 inches deep (defaults): 32 cu ft = 1.19 cu yd; with the 10% settling allowance, 35.2 cu ft → 24 bags of 1.5 cu ft, or order 1.5 cu yd bulk and have a little left for the pots. The raw bag math without settling was 22 bags — the difference between a bed that’s full in May and one that’s two inches low by July.
  • Four matching beds: set the count to 4 → 128 cu ft = 4.74 cu yd (5.2 with allowance). At this scale the comparison flips hard: roughly 95 bags at retail versus a single bulk delivery — typically half the cost or less, and one wheelbarrow marathon instead of a trunk full of plastic.
  • Topdressing 500 sq ft of lawn at ½ inch: enter 25 × 20 ft at 0.5 in → 20.8 cu ft = 0.77 cu yd. This is the workload sweet spot for bagged compost if access is tight, bulk if a truck can reach the pile point.

Bagged vs Bulk: The Real Decision

Bagged soil costs more per cubic foot — often 3–6× the bulk price — and buys consistency (screened, blended, weed-seed-light mixes), cleanliness, and carry-it-where-you-need-it convenience. Bulk soil from a landscape yard is dramatically cheaper and dramatically variable: ask what the blend is (topsoil/compost ratios vary from 70/30 to pure screened topsoil), look at it before paying, and confirm the yard’s “yard” is a true 27 cu ft scoop bucket measurement. For raised beds specifically, the popular recipe is roughly 60% topsoil, 30% compost, 10% aeration material (perlite, pumice or coarse vermiculite) — whether you buy it pre-blended as “raised bed mix” or assemble it from bulk components.

Weight matters for logistics: a cubic foot of moist soil weighs 40–75 lb depending on blend and water content, so a 1.5 cu ft bag is a 60–100 lb commitment and a cubic yard delivered is a ton-plus pile. Plan the wheelbarrow route, not just the order.

Soil Handling Discipline

  • Fill beds in two lifts. Half the soil, water deeply to settle, then the rest — the settling allowance becomes top-up material instead of a mid-season second order.
  • Never order by the “scoop” without asking its size. Skid-steer buckets run ½ to 1 yard; confirm before comparing prices.
  • Keep a reserve. Soil projects always find a second hole — a low spot by the fence, pots that need refreshing. The leftover from a bulk order is the cheapest inventory in gardening.
  • Mulch is a separate order. The 2–3 inches of mulch on top of a filled bed is its own volume (run this calculator again at mulch depth) and its own material choice.
  • Screen questionable fill. Free “fill dirt” is subsoil, not garden soil — fine for raising grade under a bed, wrong as the growing medium itself.

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Frequently Asked Questions

How much soil do I need for a 4×8 raised bed?

At 12 inches deep: 4 × 8 × 1 ft = 32 cubic feet = 1.19 cubic yards. Add the settling allowance this calculator applies (10% default) and the practical order is about 35 cu ft — 24 bags of the common 1.5 cu ft size, or 1.5 yards bulk with a little spare. At 8 inches deep instead, it’s 21.3 cu ft (0.79 yd) before settling. Depth is doing all the work in this math, so measure the bed’s inside dimensions and honest fill depth first.

How many bags of soil are in a cubic yard?

A cubic yard is 27 cubic feet, so it equals 27 bags of 1 cu ft, 18 bags of 1.5 cu ft, or 13.5 bags of 2 cu ft — before any settling allowance. This is the conversion that makes bulk pricing click: when a yard of bulk blend costs what 8–10 retail bags cost, any project beyond a dozen bags is usually cheaper delivered in bulk, access permitting.

Why does soil settle, and how much extra should I buy?

Fresh soil is full of air gaps between particles; watering and gravity collapse them, and organic matter begins decomposing immediately. Expect roughly 5–15% volume loss in the first weeks depending on blend (compost-heavy mixes settle most). The calculator’s 10% default is a sensible middle; fill in two watered lifts and the “loss” mostly happens before planting instead of after.

What’s the difference between topsoil, garden soil and raised-bed mix?

Topsoil is the screened upper layer of earth — the base ingredient, variable in quality and often low in organic matter. Garden soil is topsoil amended with compost and conditioners for in-ground beds. Raised-bed mix is a purpose blend (commonly ~60% topsoil, 30% compost, 10% aeration) engineered to stay loose in a contained box where native drainage is absent. Potting mix contains no mineral soil at all. The volumes from this calculator are the same regardless; what changes is which product fills them.

How deep should soil be in a raised bed?

For vegetables, 10–12 inches supports root crops and heavy feeders; leafy greens and herbs manage in 6–8 inches; flowers are happy at 8. Beds taller than 12 inches don’t need to be soil all the way down — the bottom can be filled with logs, branches and yard waste (hügelkultur-style) or clean fill, with the full soil depth reserved for the top foot where roots actually live. Enter only the soil depth into the calculator, not the bed’s wall height.

How much does a bag of soil weigh?

More than it looks: roughly 40–75 lb per cubic foot depending on moisture and blend, so a 1.5 cu ft bag is typically 60–100 lb and a 2 cu ft bag can exceed what one person should carry far. If the project total is over a cubic yard, delivery stops being a luxury — it’s 2,000+ lb of material that has to move from curb to bed regardless of packaging.

Can I use this calculator for compost or mulch?

Yes — the volume math is identical for any loose material: compost topdressing, mulch layers, even sand or gravel bedding (though our dedicated mulch and gravel calculators carry material-specific defaults). Just enter the area and the depth of that layer. A 3-inch compost amendment over a 10 × 10 ft bed is 25 cu ft, and a 3-inch mulch layer over the same bed is another 25 cu ft — layers stack additively, which is exactly why beds “eat” more material than first estimates suggest.

Is this soil calculator free?

Yes — free, instant, no sign-up. Enter dimensions and depth and get cubic feet, cubic yards and bag counts with settling included.