How Much Topsoil Do I Need?

Topsoil is the one landscaping material where the right amount can vary by a factor of fifty. A quarter inch raked over a tired lawn barely fills a pickup bed, while a new lawn or a set of raised beds can call for a full dump truck. That range is why guessing goes so badly. This guide works through the most common topsoil projects one at a time, with real measurements and totals, so you can see which numbers matter for your job and how much topsoil to order.

The Formula in One Line

Multiply the area in square feet by the depth in inches, then divide by 324. The result is in cubic yards. If you want to know where 324 comes from, or need to work with circles and metric units, our cubic yard calculation guide explains it in full. The rest of this article is about the decisions that feed into that formula, because with topsoil, getting the depth and the type of soil right matters far more than the arithmetic.

Topsoil, Garden Soil or Fill Dirt?

Before you work out quantities, make sure you are ordering the right product. Suppliers use these names loosely, so ask what is actually in the mix.

A common money-saver on big jobs is to use cheaper fill dirt for the bottom of a deep fill and finish with a few inches of good topsoil. In that case, calculate the two layers separately, since they come from different piles and are often priced differently.

How Deep Should Topsoil Be?

Depth is the decision that moves your total the most. These are figures many gardeners and landscapers work with, but your soil, climate and plants all play a part.

Calculating Topsoil for Common Projects

A new lawn

A backyard 40 ft long and 30 ft wide covers 1,200 square feet. At 6 inches deep, that is 1,200 × 6 ÷ 324 = 22.22 cubic yards. A job this size usually arrives in more than one truckload, so ask the supplier how many loads it will take and whether they can schedule them back to back. If the existing ground is reasonable, you might lay 4 inches instead, which drops the order to 14.81 yards and saves a significant amount.

Top-dressing an existing lawn

Top-dressing means raking a thin layer over grass to smooth out bumps and improve the surface. Over a 2,000-square-foot lawn at a quarter inch, you need 2,000 × 0.25 ÷ 324 = 1.54 cubic yards. Thin layers like this are easy to overestimate. People often order three or four yards, then struggle to spread it without smothering the grass. For top-dressing, a fine screened soil or a soil and compost blend is the usual choice.

An in-ground vegetable plot

A plot 20 ft by 10 ft dug and refilled 8 inches deep needs 200 × 8 ÷ 324 = 4.94 cubic yards. That is a lot of soil to replace. If the existing ground is decent, many gardeners keep it and add a 3-inch layer of good soil or compost on top to work in. That needs only 200 × 3 ÷ 324 = 1.85 cubic yards, well under half the amount.

A set of raised beds

Raised beds add up quickly because you are filling the whole frame. Three beds, each 10 ft by 4 ft and 12 inches tall, hold 10 × 4 × 1 = 40 cubic feet apiece, so 120 cubic feet in total. That is 4.44 cubic yards. In bags of 0.75 cubic feet, it would take 160 bags. Seeing that number on paper is usually what convinces people to order in bulk. Raised beds are typically filled with a blended garden soil rather than plain topsoil, so ask for a mix suited to vegetables.

Leveling a bumpy yard

Low areas rarely have an even depth, so a single measurement is not enough. Stretch a string line level across the dip, then mark out a rough grid and measure the gap between the string and the ground at each point. Say a low area 15 ft by 12 ft gives readings of 2, 4, 5, 3, 1 and 3 inches. The average is 18 ÷ 6 = 3 inches, so you need 180 × 3 ÷ 324 = 1.67 cubic yards. More grid points give a better average on larger areas.

Planning for Settling

Freshly delivered topsoil is loose and full of air. Once it has been rolled, walked on and rained on, it sits lower than when it was spread. Thin top-dressing layers barely change, but deep fills can drop noticeably over the following weeks.

There are two practical ways to deal with this. One is to order a little more than your calculated volume and spread the soil slightly above the finished height, letting it settle down to level. The other is to fill to grade, water thoroughly, wait for it to settle and then top up the low spots. The second takes longer but avoids guesswork. The Topsoil Calculator has an optional waste field if you want to build an allowance into your figure.

Bulk or Bagged Topsoil?

Bagged topsoil and garden soil are convenient for small jobs: a couple of planters, one raised bed or patching a few bare spots. They are clean to handle and easy to store, and you can buy exactly what you need.

Beyond a yard or so, bulk delivery usually makes more sense on both cost and effort, as the raised bed example above shows. Before ordering, ask whether the soil is screened, whether it is sold by the yard or the ton, and whether there is a minimum load. Topsoil is heavy, especially after rain, so if you are collecting it yourself, check the weight first using our cubic yards to tons guide.

Checking Topsoil Quality Before You Buy

Cheap topsoil can turn out to be expensive if it is full of rubble or weed roots. If you can, visit the yard and look at the pile before you order.

• Look at the texture. Good topsoil is dark and crumbly. Squeeze a damp handful: it should hold together loosely and break apart when poked, not form a sticky ball.
• Check for debris. Stones, roots, plastic or construction waste suggest the soil has not been screened properly.
• Smell it. Healthy soil smells earthy. A sour or chemical smell is a warning sign.
• Ask about testing. Some suppliers can share basic test results for pH and nutrients, which is useful for vegetable gardens.
• Watch for weeds. A pile covered in sprouting weeds will bring those seeds into your garden.

Topsoil Mistakes to Avoid

• Burying sod instead of removing it. Spreading topsoil over thick turf can leave a matted layer underneath. Strip or till it first for new lawns.
• Raising the grade against the house. Keep finished soil sloping away from the foundation and below siding so water drains away from the building.
• Piling soil over tree roots. A thick new layer over an established tree's root zone can harm it. Leave existing trees at their current grade if you can.
• Leaving a hard boundary between layers. Mix the first inch or two of new soil into the existing ground so water and roots pass through easily.
• Forgetting soil you already have. Soil dug from a patio or path project can often be reused elsewhere, reducing what you need to buy.

Frequently Asked Questions

How much topsoil do I need for a 10 × 10 area?

A 10 ft by 10 ft area is 100 square feet. At 6 inches deep, that is 100 × 6 ÷ 324 = 1.85 cubic yards. At 4 inches it is 1.23 cubic yards.

Can I put topsoil directly over grass?

A thin top-dressing of a quarter to half an inch can go straight over grass, and the lawn will grow through it. Thicker layers will usually smother the grass underneath, so for a full new lawn it is better to remove or till the old turf first.

When is the best time to spread topsoil?

When the ground and the soil are reasonably dry. Wet topsoil is heavy, clumps together and compacts under your feet and the wheelbarrow. For new lawns, many people time the work so they can seed in a mild season afterward.

Is screened topsoil worth the extra cost?

For lawns, top-dressing and beds, usually yes. Screening removes stones and roots that would otherwise have to be picked out by hand. For filling deep holes that will be capped with better soil, unscreened soil or fill dirt is often fine.

Should I mix new topsoil with my existing soil?

Working the new soil into the top few inches of the old ground helps avoid a sharp layer that can slow drainage and root growth. It also lets you get away with a thinner layer of new soil in many cases.

Final Thoughts

Topsoil estimates go wrong for two reasons: the wrong depth and the wrong product. Pick the depth that suits your project, choose the right soil, measure carefully and the cubic yards follow. The Topsoil Calculator does the sums for any shape, and the Square Feet Calculator helps when you only need the area. Once the soil is down, our guide to how much mulch you need covers the finishing layer for beds, and the gravel guide is there if paths are next on the list.