How to use the soil calculator
Pick the tab that matches the job. Raised beds is for a bed with sides: type its size, its height and how far below the rim the soil should stop, choose a mix, and get how much of each ingredient to buy. Fill dirt covers a hole, a low spot or a grade, or digging soil out and hauling it away. Pots and planters adds up potting soil. Weight and loads turns a volume into tons, pickup loads and wheelbarrow trips. Nothing leaves your device unless you make a share link. Lawns are a different job with their own thin-layer rules, so they live on the topsoil calculator.
How it is figured
cubic feet = area (sq ft) × soil depth (ft) × (1 + settling)
cubic yards = cubic feet ÷ 27
A cubic yard is 3 × 3 × 3 feet, or 27 cubic feet. The page works out each bed's area (length × width, π × diameter² ÷ 4 for a round bed, or the L-shape's outer rectangle minus the notch) and multiplies by the depth the soil really fills.
Worked example. A bed 8 feet long and 4 feet wide is 12 inches high, and you want the soil 2 inches below the rim. The soil is 10 inches deep, which is 0.833 foot. The bed holds 32 × 0.833 = 26.67 cubic feet, or 0.99 cubic yard. Add 15 percent for settling and you order 30.67 cubic feet, or 1.14 cubic yards. The 60/30/10 mix is 18.4 cubic feet of topsoil, 9.2 of compost and 3.07 of sand, or 21 bags of 1.5 cubic feet.
Mixes for raised beds
No single mix suits every bed, so every percent is editable, by volume rather than weight. A common vegetable-bed recipe is 60 percent topsoil, 30 percent compost and 10 percent coarse material such as sand. The University of Maryland Extension suggests roughly 25 to 50 percent organic matter by volume when a bed is filled with garden soil, and the page flags a mix outside that range. The popular "Mel's Mix" from the Square Foot Gardening books is a different idea: equal parts compost, peat moss and coarse vermiculite, with no topsoil. It is a popular recipe, not a research result, so the page does not hold it to the extension range. Percents that do not add to 100 are scaled, and the page says so.
Logs and branches in the bottom
Some gardeners fill the bottom of a deep bed with logs and branches, the idea behind hügelkultur. Clemson's extension notes this can cut the soil and compost a deep bed needs, and that the wood breaks down so the bed shrinks. Type the depth of the wood and the page takes that layer out of the soil volume and reports it separately. Because it rots, keep the settling percent generous.
Fill dirt: bank, loose and compacted
Dirt still in the ground is measured in bank yards. Dug up, it fluffs into more loose yards than the hole it came from. Caterpillar's earthwork tables give a load factor, bank volume divided by loose volume: 0.81 for loam, 0.82 for natural clay and 0.89 for dry sand. Divide the bank yards by the factor to get what you will haul: 10 × 10 feet dug 3 feet deep is 11.11 bank yards, or 13.72 loose yards of loam. Fill goes the other way: it arrives loose and packs down when spread and tamped, so you order more than the finished volume. The 20 percent start is a planning estimate, not a table value. Filling 1,000 square feet 6 inches deep is 500 cubic feet, or 18.52 yards, and 22.22 yards with that 20 percent.
Pots and planters
A round pot is wider at the top, so its volume is a cone with the tip cut off, worked from the diameter at the soil line and at the bottom. A box planter is length × width × soil height. For grow bags, type the label size; labeled gallons are nominal, so the real volume may differ. Small bags of soil are sold in quarts. A quart on a bag is a dry quart, one thirty-second of a bushel, which is 67.2 cubic inches; 25.7 of them make a cubic foot.
Where the numbers come from
Weights per cubic yard are the planning numbers on the topsoil and sand calculators, in US tons of 2,000 pounds: screened topsoil 1.15 tons dry and 1.5 wet, garden mix 0.95 and 1.25, fill dirt 1.2 and 1.55, compost 0.5 and 0.7, and sand 1.35 and 1.55. A supplier's figure or a weighed load beats any of them. Perlite, bark, peat and vermiculite have no weight here because the page has no verified figure for them, so a bed with them shows volumes only. Pickup payload is the number you type; check the sticker in your door jamb. A foot is exactly 0.3048 meter, so a cubic yard is exactly 0.764554857984 cubic meter. No building code covers how much soil a garden needs; where a bed or wall holds back earth, your local code and an engineer decide.
What people use it for
New raised beds, ordered by the yard or by the bag; low spots and grades; digs that need hauling; a deck full of containers; and checking that a pickup can carry the order, or how many wheelbarrow runs it takes.
Common mistakes
- Using the outside height. Measure inside, from the ground to the rim, and decide how far below the rim the soil should stop.
- Forgetting settling. Fresh soil drops after watering, and a bed filled to the brim in spring is low by summer.
- Mixing up bank and loose yards. A hole's volume and a truck's load are not the same.
- Counting heavy soil by volume only. A pickup that holds two yards of mulch may carry one of wet topsoil.
Questions
How much soil do I need for a raised bed?
Multiply length × width × the soil depth in feet, then divide by 27 for cubic yards. A 4 × 8 foot bed with 10 inches of soil is about 0.99 cubic yard before settling.
How many bags make a cubic yard?
Divide 27 by the cubic feet on the bag. For 1.5 cubic foot bags that is 18 bags, and for 2 cubic foot bags it is 13.5, so buy 14. Type your bag size and the page counts the bags for your whole job.
Can I use metric?
Yes. Press Metric to type meters, centimeters and liters. Results lead with cubic meters and still show cubic yards, because soil is sold by the yard in the US.
Can I share my result?
On the Raised beds and Fill dirt tabs, yes: a link with a picture for Facebook, a link you can copy, and a short video for TikTok. The link keeps the shapes, sizes, mix and settling percent for 90 days, never a price.