How to use the topsoil calculator
- Enter the length and width of the area.
- Enter the finished depth you want after the soil has settled.
- Add extra for settling. Loose soil sinks once it is watered and walked on; set this to 0 if you will compact it as you spread.
- Enter the bag size if you are buying bags.
New beds settle after the first heavy watering, which is why Decoratoradvice suggests checking the depth again a week after you spread the soil.
Topsoil formula
Volume = length × width × depth × (1 + settling extra)
Cubic yards = cubic feet ÷ 27
Bags = cubic feet ÷ bag size, rounded up
Worked example
A new lawn area 30 × 20 ft, 4 in of topsoil, 10% extra for settling:
30 × 20 × 0.333 = 200 cu ft
With 10% extra: 220 cu ft
220 ÷ 27 = 8.15 cu yd
In 1 cu ft bags: 220 bags
At that volume, bulk delivery is far more practical than bags.
Raised beds
For a raised bed, enter the inside length and width and the depth of soil you want. A 8 × 4 ft bed filled 10 in deep holds 26.7 cu ft before settling, about 1 cu yd. Many gardeners mix topsoil with compost for beds; the volume is the same either way.
Tips
- Remove sod, roots and debris before spreading new soil.
- Spread in layers and water lightly between them to settle the soil before final grading.
- Grade soil away from the house foundation.
- Finish a new lawn with sod using the sod calculator, or mulch a new bed with the mulch calculator.
Common mistakes
- Ordering the loose volume you need after settling without extra, then coming up short.
- Leaving depth in inches when multiplying.
- Burying plant crowns or tree roots under new soil.
Frequently asked questions
How much topsoil do I need for a new lawn?
Multiply the lawn area by the depth you plan to add. For a 30 × 20 ft area at 4 in, 200 cu ft, or about 8.15 cu yd with 10% extra.
How much area does a cubic yard of topsoil cover?
At 4 in deep, 81 sq ft; at 2 in, 162 sq ft. The cubic yard calculator has more depths.
How many bags of topsoil are in a cubic yard?
27 bags of 1 cu ft, or 36 bags of 0.75 cu ft.
Why add extra for settling?
Loose soil contains air. Once watered and walked on, it compacts and the surface drops.
Can I use this to backfill a retaining wall?
Yes, for the soil above the drainage zone. Plan the wall and its drainage stone with the retaining wall calculator.
Key takeaways
- Cubic yards = length × width × depth (in feet) × (1 + settling) ÷ 27.
- Plan for the finished depth after settling.
- One cubic yard covers 81 sq ft at 4 in deep.
- Bulk delivery is usually better than bags for more than a cubic yard or two.