Soil Calculator

What formula does the soil calculator use?

The calculator finds the bed's area, multiplies it by fill depth, and repeats that volume for identical beds. Your chosen settling allowance is added afterward, so both raw volume and order volume remain visible.

A rectangle measuring 10 feet long and 8 feet wide has an area of 80 square feet. A 6-inch layer equals 0.5 feet, so the unadjusted volume is 80 × 0.5 = 40 cubic feet. Dividing by 27 gives about 1.48 cubic yards. A 10% allowance changes the order estimate to about 1.63 cubic yards.

That last percentage is not hidden inside the formula. Soil mixes, project conditions, compaction, and supplier increments differ, so the tool lets you choose the allowance instead of pretending one number suits every project.

How should you measure a garden bed for soil?

Measure the inside planting area and only the vertical space that still needs soil. Do not automatically use the full height of a raised-bed frame when existing soil, compost, roots, or another layer already occupies part of it.

1. Choose the closest shape. Use rectangle for square or rectangular beds, circle for round planters, and known area for irregular spaces you have already mapped.
2. Measure the internal dimensions. Frame thickness does not hold soil, so measuring the outside edges can overstate the usable volume.
3. Measure the missing depth. Check several points if the current surface is uneven and use a practical average.
4. Count matching beds. Use the quantity field only when their dimensions and fill depths are genuinely the same.
5. Confirm the supplier's selling unit. Read the bag label or ask whether bulk material is sold by cubic yard, cubic meter, half-yard, or another increment.

Split an L-shaped or curved garden into smaller rectangles and circles, calculate each part, and add the results. This usually gives a more transparent estimate than forcing an awkward boundary into one oversized rectangle.

For a freeform edge, follow the field steps in How to Measure an Irregular Garden Bed, then enter the checked square footage through known area.

How do cubic feet, cubic yards, liters, and cubic meters relate?

One cubic yard contains exactly 27 cubic feet. One cubic meter contains 1,000 liters, while one cubic yard equals about 0.7646 cubic meter or 764.6 liters.

GardenMeasure converts through a common base volume so the imperial and metric results describe the same physical space. The conversion constants follow the NIST Guide to the SI and NIST's volume tables. NIST defines the international foot as exactly 0.3048 meter; cubing that length gives the cubic-foot-to-cubic-meter relationship.

Keep area and depth in matching systems before doing the manual calculation. If your area is in square feet and depth is in inches, divide depth by 12 first. If area is in square meters and depth is in centimeters, divide depth by 100.

Should you buy bagged soil or bulk soil?

Compare the total project cost, not only the advertised unit price. Bagged soil needs whole-bag rounding; bulk soil may add delivery fees, minimum orders, and half-yard or whole-yard ordering rules.

The calculator multiplies bag price by the rounded-up bag count. It multiplies the exact adjusted volume by your bulk unit price and adds delivery. Before buying, replace that exact bulk result with the supplier's actual order increment. A calculated 1.63 cubic yards may need a 2-yard order if the yard only sells whole units.

At what volume does bulk beat bags?

Bulk wins only after the order is large enough to repay the delivery fee.

Break-even bags = delivery fee ÷ (price per bag − bag volume × bulk price per cubic yard), rounded up to whole bags. Break-even volume = break-even bags × bag volume. Below that volume, whole bags cost less. Above it, bulk delivered costs less. The calculator works this out live from your prices above.

Supplier minimums, half-yard increments, taxes, and delivery zones are not in this sum. Confirm them with the supplier before ordering.

Is topsoil the same as garden soil or potting mix?

Topsoil generally refers to mineral soil, while bagged garden, raised-bed, and potting products can contain different blends. Choose the product for the site before calculating its volume.

The topsoil, garden soil, and compost comparison matches low spots, established beds, raised beds, lawns, and containers with the right starting material. It also lists the label, source, and supplier details to check.

Use the Raised Bed Soil Calculator when you buy separate components. This Soil Calculator remains the better choice for one complete blend used across a general garden area.

If compost is an amendment rather than the main fill, the compost topdressing and mixing guide explains when it belongs on the surface and when a pre-plant soil zone may be incorporated.

Why does the calculator use a custom settling allowance?

A custom allowance keeps the assumption visible. The correct extra amount depends on the blend, how loosely it arrives, how you place it, and whether organic components lose volume over time.

Enter zero when you want the pure geometric volume. Add a modest percentage only when your supplier, project experience, or material specification supports it. The raw result remains on screen so you can compare the mathematical volume with the shopping estimate.

An allowance is not a substitute for correct measuring. Adding 10% to an outside-frame measurement or the full frame height can simply make an already generous estimate larger.

Why does this soil calculator not assume a weight?

Volume can be calculated from dimensions, but weight requires a reliable density for the exact material and its moisture condition. The calculator therefore shows weight only when you enter a supplier density, and shows no weight at all when the field is blank. A generic pounds-per-yard figure would create false precision.

The USDA Natural Resources Conservation Service treats bulk density and soil moisture as measured properties. Its educator material calculates dry bulk density from dry soil weight and core volume, while water content depends on the difference between moist and oven-dry weight.

Ask the seller for the material's current weight or density if you need to check trailer payload, vehicle limits, lifting safety, or structural loading. Those decisions should not rely on a universal topsoil-weight assumption.

The cubic-yard soil weight guide works one example through in full: at 72 pounds per cubic foot, one cubic yard weighs 27 × 72 = 1,944 pounds, and 1.5 cubic yards weigh 2,916 pounds. The same guide shows moisture adding 15 percent of dry mass in its example, taking 1,944 pounds to 2,235.6 pounds. Those are worked examples for one stated condition, not a weight for your soil. The calculator repeats the same two figures for your volume in the result above, labelled as an illustrative example.

Worked soil calculation example

A 12-by-4-foot raised bed filled to 10 inches needs about 40 cubic feet, or 1.48 cubic yards, before any allowance. The same volume is about 1.13 cubic meters or 1,133 liters.

1. Area: 12 ft × 4 ft = 48 sq ft.
2. Depth: 10 in ÷ 12 = 0.8333 ft.
3. Volume: 48 sq ft × 0.8333 ft ≈ 40 ft³.
4. Cubic yards: 40 ft³ ÷ 27 ≈ 1.48 yd³.
5. With a 10% allowance: 1.48 yd³ × 1.10 ≈ 1.63 yd³.

If each bag contains 1.5 cubic feet, the adjusted 44 cubic feet requires 30 bags because 44 ÷ 1.5 = 29.33 and partial bags are not normally purchased. Enter the real bag volume and price printed by the seller to compare it with a delivered bulk quote.