Topsoil Calculator
Estimate how much topsoil you need for a rectangular, circular, or known area. Enter the soil depth, material, bag size, and optional price to see volume, weight, whole bags, and cost.
Estimate Soil Volume, Weight, Bags, and Cost
Topsoil Formula
Where:
- \(A_{\mathrm{ft}^2}\) — area in square feet: length × width for a rectangle, \(\pi D^2/4\) for a circle, or the entered known area
- \(d_{\mathrm{ft}}\) — soil depth in feet
- \(c\) — compaction allowance as a percentage
- \(V\) — material volume, including the allowance
- \(\rho\) — material bulk density in US tons per cubic yard
- \(B_{\mathrm{ft}^3}\) — volume of one bag in cubic feet; \(N\) is the number of whole bags
The calculator converts your measurements to consistent units, then adds the allowance to the volume. Weight and bag count are based on that increased volume.
Topsoil – Calculation Example
Example: Cover a 10 ft by 10 ft rectangle with 4 in of topsoil. Use the default 10% compaction allowance, 2 cu ft bags, a bulk density of 1.1 US tons per cu yd, and a price of $45 per cu yd.
\[A=10\times10=100\ \mathrm{sq\ ft},\qquad d=\frac{4}{12}=\frac13\ \mathrm{ft}\]
\[V=100\times\frac13\times1.10\approx36.667\ \mathrm{cu\ ft}=1.358\ \mathrm{cu\ yd}\]
\[W\approx1.35802469\times1.1=1.494\ \mathrm{US\ tons},\qquad N=\left\lceil\frac{36.6667}{2}\right\rceil=19\ \mathrm{bags}\]
\[\text{Estimated cost}=1.35802469\times\$45=\$61.11\]
Result: About 1.358 cu yd (36.667 cu ft) of topsoil, weighing approximately 1.494 US tons. That is 19 whole 2 cu ft bags; at $45 per cu yd, the estimated material cost is $61.11.
How to use the calculator
- Choose an Area shape. For Rectangle, enter Length and Width and select a unit for each. For Circle, enter Diameter. If you have already measured the surface, choose Known area and select its Area unit.
- Enter the finished layer thickness in Soil depth and choose inches or centimeters under Depth unit. Use a depth greater than zero.
- Choose a Material. If you select Custom density, enter your supplier’s figure in Custom bulk density, measured in US tons per cu yd.
- Select the Bag size you might buy, then set a Compaction allowance from 0% to 100%. The default 10% adds material for settling and small variations in the surface.
- Optionally enter Price (optional) and choose a Price basis of dollars per cu yd or dollars per bag. Clear the price field if you do not want a cost estimate.
Read Material volume in cu yd, cu ft, or m³ according to how your supplier sells soil. The results also show Estimated weight in US tons and tonnes, Whole bags needed, and, when you provide a price, Estimated material cost.
What the topsoil estimate means
Topsoil is commonly spread to build up planting areas or improve an existing surface. The amount needed depends on the area covered and the depth of the new layer. A broad, shallow layer can require as much material as a smaller, deeper bed, so measuring both matters before ordering.
Material volume is the amount to purchase after the compaction allowance has been added. The calculation starts with area multiplied by depth, then increases that volume by the selected percentage. For a rectangular area, measure its two sides; for a circular area, measure across its center. If a space is irregular, divide it into simpler shapes, add their areas, and enter the total under Known area.
Estimated weight helps when checking delivery or vehicle capacity, but it is less certain than volume. The calculator uses approximate bulk densities of 1.1 US tons per cu yd for topsoil, 0.9 for garden soil, 0.5 for compost, and 1.35 for sand. A US ton is 2,000 lb; a tonne is 1,000 kg. The weight estimate includes the compaction allowance.
Whole bags needed rounds up because bags are sold as complete units. Cost follows the selected price basis: per-cubic-yard pricing uses the unrounded volume, while per-bag pricing uses the whole-bag count. A per-yard quote and a per-bag quote therefore describe different purchasing options, even when both refer to the same calculated volume.
Assumptions and practical tips
Measure the depth of the new soil layer, not the full depth of an existing bed. The estimate assumes that depth is uniform across the measured area. If the ground is uneven, take several depth measurements and use a representative value, or calculate noticeably different sections separately.
The compaction allowance adds material; it does not predict exactly how much a particular soil will settle. The default 10% is a planning margin, not a guarantee. Moisture, composition, handling, and how firmly soil is placed can all change its bulk density and final depth. If delivery weight is important, ask the supplier for a density specific to the product and enter it using Custom density.
Check whether a bulk supplier quotes by loose cubic yard and whether bag labels state volume. The cost result covers material only: delivery, taxes, minimum-order charges, and other fees are not included. For a different ground-cover project, use the mulch calculator or gravel calculator rather than applying a topsoil density to another material.
Frequently Asked Questions
How much area does one cubic yard of topsoil cover?
One cubic yard covers about 162 sq ft at a 2-inch depth, 108 sq ft at 3 inches, or 81 sq ft at 4 inches, before any allowance for settling. To check another depth, divide 27 cubic feet by the depth in feet. Actual coverage may vary if the ground is uneven or the soil settles.
How deep should topsoil be for a new lawn or garden bed?
A new lawn often benefits from roughly 4–6 inches of suitable soil above poor subsoil, while planting beds may need a deeper usable soil layer, depending on the plants and what is already there. These are planning ranges, not universal requirements. Check the existing soil and drainage before adding material; piling topsoil over a compacted layer may not solve poor growing conditions.
How much topsoil should I spread over an existing lawn?
For lawn topdressing, use a thin layer—often about ¼–½ inch—and leave the grass blades visible. A thick layer can smother established turf. If you are filling deeper low spots, do it gradually or consider lifting and leveling the sod. Topdressing is a different job from laying several inches of soil for a new lawn.
How do I compare a 40 L or 50 L bag with a cubic-yard delivery?
A 40 L bag contains about 1.41 cu ft, and a 50 L bag about 1.77 cu ft. One cubic yard is about 765 L, equivalent by labeled volume to roughly 19.1 bags of 40 L or 15.3 bags of 50 L. You must buy whole bags, and the amount needed for your project also depends on the area and depth.
How do I estimate topsoil for a partly filled raised bed?
Measure the bed’s inside length and width, then use only the empty height you intend to fill with new soil. If that height differs across the bed, measure sections separately and add their volumes. Subtract space occupied by large structures or other fill. Make sure the planned soil depth suits the plants rather than assuming the bed must be filled to its rim.
Should I buy topsoil, garden soil, or compost?
Choose the material for its intended use, not just its estimated weight. Topsoil is used to build a soil layer; garden soil is a prepared planting mix; compost is generally mixed into existing soil as an amendment rather than used alone as a deep fill. Product contents vary, so check the supplier’s description and avoid assuming these materials are interchangeable.
Are bags or bulk topsoil cheaper?
Compare prices for the same volume, including fees. Multiply a bag’s cubic-foot volume by its price per bag to compare options, or convert a bulk quote using 27 cu ft per cubic yard. Bags may be practical for small jobs, while bulk delivery can cost less for larger ones. Include delivery charges, minimum orders, taxes, and any leftover material in the comparison.