Topsoil Calculator (2026)
Enter your bed size and depth to find out how many cubic yards and bags of topsoil you need, and whether bags or bulk delivery is cheaper.
Calculate Your Topsoil
Measure the longest side of the bed in feet.
Measure the shorter side of the bed in feet.
New garden beds usually need 6 inches; topping up an existing bed usually needs 2 to 3 inches.
Check the bag label: most garden-centre topsoil bags are 2 cubic feet.
The delivered bulk price per cubic yard from a local supplier, before any delivery fee.
The store price for one bag of the selected size.
Bulk cost is calculated from the exact, unrounded cubic yards, then rounded to cents. The cubic yards shown above are rounded to 2 decimals, so multiplying the displayed yards by the price may differ by a few cents. Bags are always rounded up: you cannot buy part of a bag.
How the Math Works
A garden bed is a rectangular box, so its volume is length times width times depth. The catch is the units: length and width are in feet, but depth is in inches, so depth must be divided by 12 first. Once you have cubic feet, divide by 27 to get cubic yards, because one cubic yard equals 27 cubic feet. Bulk topsoil is sold by the cubic yard, while bagged topsoil is sold by the bag, so this calculator uses the same cubic-yard engine as our gravel, mulch, and concrete calculators, converts the same volume both ways, and prices each option.
Volume (cu ft) = length (ft) x width (ft) x depth (in) / 12
Volume (cu yd) = volume (cu ft) / 27
Bags needed = volume (cu ft) / bag size (cu ft), rounded UP
Bags cost = bags needed x price per bag
Bulk cost = exact volume (cu yd) x price per cubic yard
How Deep Should Topsoil Be?
Depth is the single biggest driver of how much topsoil you need. Doubling the depth doubles the volume for the same bed, so it pays to match the depth to the job rather than guessing. This table shows the depths most garden jobs call for.
| Project | Typical depth | Why |
|---|---|---|
| Topping up an existing lawn or bed | 2 to 3 inches | Refreshes the surface without burying existing plants |
| New flower or vegetable bed | 6 inches | Enough root depth for most annuals and vegetables |
| New lawn from seed or sod | 4 to 6 inches | Grass roots establish best in at least 4 inches of good soil |
| Raised bed fill | 8 to 12 inches | Deeper root runs for vegetables and perennials |
| Levelling a bumpy lawn | 1 to 2 inches at a time | Thick layers smother grass, so level in thin passes |
Worked Example: 20 x 10 Foot Bed, 6 Inches Deep
| Calculation | Result | |
|---|---|---|
| Bed area | 20 x 10 | 200 sq ft |
| Volume in cubic feet | 20 x 10 x (6 / 12) | 100 cu ft |
| Volume in cubic yards | 100 / 27 | 3.70 cu yd |
| 2 cu ft bags needed | 100 / 2, rounded up | 50 bags |
| Bags cost | 50 x $5 | $250.00 |
| Bulk cost | 3.7037 x $40 (exact yards) | $148.15 |
| Cheaper option | $148.15 is less than $250.00 | Bulk topsoil |
Bulk wins by about $100 in this example, before delivery fees. That gap is typical: bagged soil carries packaging and retail markup on every bag, while bulk soil is priced by the yard. Bags still make sense for small beds, top-ups, and gardens a delivery truck cannot reach.
Topsoil Bag Chart: Common Bed Sizes at 6 Inches Deep
These figures use 2 cubic foot bags and a 6-inch depth, the most common garden-bed setup. Use the calculator above for any other size, depth, or bag size.
| Bed size | Area | Cubic yards | 2 cu ft bags |
|---|---|---|---|
| 10 x 10 ft | 100 sq ft | 1.85 cu yd | 25 bags |
| 10 x 20 ft | 200 sq ft | 3.70 cu yd | 50 bags |
| 20 x 20 ft | 400 sq ft | 7.41 cu yd | 100 bags |
| 20 x 30 ft | 600 sq ft | 11.11 cu yd | 150 bags |
| 30 x 40 ft | 1,200 sq ft | 22.22 cu yd | 300 bags |
Order About 10% Extra for Settling and Waste
Fresh topsoil settles as it is watered and walked on, and some is always lost to spillage, uneven ground, and wheelbarrow runs. The standard advice is to order about 10% more than the calculated volume. This is a guide note only: the calculator above shows the exact calculated volume, and the 10% allowance is NOT included in its results, so add it yourself when you order. For the example bed, 10% extra means ordering about 4.07 cubic yards instead of 3.70, or buying 55 bags instead of 50. Running short halfway through a bed is far worse than having a little left over, because a thin patch shows up as weak growth all season.
Bags vs Bulk: Which Should You Choose?
- Choose bags for small jobs. Under about one cubic yard, a few bags carried by hand are simpler and cheaper than a truck delivery, which often carries a minimum-load or delivery fee.
- Choose bulk for anything over about two cubic yards. The per-yard price is usually far lower, and a delivery drops the whole load where you need it.
- Check truck access. If a delivery truck cannot reach the bed, bags may be your only option, or you may need to wheelbarrow bulk soil from the drop point.
- Count your labor. Hauling and opening 50 bags is a full afternoon of work. A bulk delivery skips the packaging entirely.
- Compare delivered prices, not just material prices. Bulk quotes may add a delivery fee, and bag prices may not include tax. Put the all-in numbers into the calculator for a fair comparison.
- Check quality before a big bulk order. Ask what the mix contains, and look for weed seeds, rubble, or clay lumps. Cheap bulk soil that needs replacing costs more than good soil bought once.
