Topsoil Calculator
Yards or bags of screened topsoil by area and depth
What is topsoil calculator?
A topsoil calculator answers the homeowner’s first question on any lawn prep or garden amendment project: how many cubic yards (or bags) do I need. The volume math is straightforward — area times depth — but bagged topsoil at retailers comes in three different bag sizes (0.75, 1, and 1.5 cu ft), and the conversion to bag count varies accordingly.
The default density is 80 lb/ft³ for screened topsoil at moderate moisture content. Heavy clay-rich topsoil runs 100-110 lb/ft³ and weighs about 30% more per yard; light sandy loam closer to 70 lb/ft³. Volume math doesn’t change with soil type; only the weight readout differs.
What depth to choose? Six inches is the textbook minimum for new-lawn prep over compacted clay sub-soil — anything less and grass roots can’t penetrate. Four inches works over softer, well-drained sub-grade. For amending existing beds, 2-3 inches mixed into the top 4-6 inches of native soil. For lawn top-dressing or overseeding, a quarter to half inch is plenty — anything thicker smothers the existing grass.
Bulk vs bagged: at landscape supply yards, bulk topsoil typically runs ~$25-45 per cubic yard delivered. A cubic yard equals 27 of 1-cu-ft bags or 36 of 0.75-cu-ft bags. By the time you’re past 2 yards (~50 bags), bulk wins on price and saves the lifting. Below that, bags are easier — and bag-quality screened topsoil is often cleaner than bulk.
The 10% waste factor default covers spillage during transfer and minor spread loss. For raised beds that will compact and settle in the first month, bump to 15-20% so you have extra to top off. Topsoil settles 10-15% under watering; fresh-filled beds always look a little under-filled by mid-season.
When to use a topsoil calculator
- New lawn prep — Spread 4-6 inches of screened topsoil over a graded sub-base before seeding or sodding. Output in yards matches landscape supply pricing.
- Bed amendment — Add 2-3 inches of topsoil to existing beds before fall planting. The calculator handles partial coverage on irregular shapes.
- Top-dressing a thin lawn — 1/4 to 1/2 inch over an existing lawn for overseeding. Even a small lawn needs more topsoil than the depth suggests.
How to use the Topsoil Calculator
- Measure the area — For lawn prep and rectangular beds, multiply length by width. For irregular yards, break into rectangles and sum. Don't forget to subtract footprints of buildings, paved areas, or trees.
- Pick a depth — Use 4-6 inches for new lawn prep over rough grade. 2-3 inches for amending existing beds. 1/4 to 1/2 inch for top-dressing an established lawn — anything thicker smothers the grass.
- Read the bag count — Output shows bags of the size you selected (1-cu-ft is the retail standard for topsoil; 0.75-cu-ft and 1.5-cu-ft are also common). Round up — partial bags don't store outdoors.
- Apply waste factor — 10% covers spillage during transfer and minor spread loss. Bump to 15-20% for raised-bed fills where you may want extra to top off after the first month's settling.
Worked examples
1000 ft^2 new lawn at 4 in
Input: 20 ft x 50 ft x 4 in depth
Output: 12.3 cu yd / 333 of 1-cu-ft bags (with 10% waste)Garden bed amendment
Input: 10 ft x 12 ft x 3 in depth
Output: 1.11 cu yd / 30 of 1-cu-ft bagsMix the topsoil into the existing 4-6 inches for best root contact.
Lawn top-dress, 500 ft^2 at 0.5 in
Input: 20 ft x 25 ft x 0.5 in depth
Output: 0.77 cu yd / 21 of 1-cu-ft bags