Landscaping on a Budget: Calculating Mulch, Gravel, and Ground Cover

The landscaping trap nobody warns you about

When I tackled the front yard of my bungalow a few years back, I made the classic mistake. I drove to the garden centre, pointed at a pile of bark mulch, and said “give me ten bags.” I had no idea how much ground I was covering. I ran out halfway across the front beds, went back for another ten bags, and still ended up with bare patches along the fence line. Three trips to the garden centre for one job. That’s not a renovation — that’s a shuttle service.

Landscaping materials are sold by volume, and most people have no intuition for how far a cubic yard of mulch actually spreads. The maths isn’t complicated, but you have to do it before you load up the truck. This guide walks through the three ground-cover materials I use most — mulch, gravel, and general area coverage — and gives you the calculators to nail the quantities on the first pass.

Know your square footage first

Before you can figure out how much mulch or gravel to buy, you need to know the area you’re covering. This sounds obvious, but it trips people up more than you’d expect. Garden beds are rarely neat rectangles. They curve around trees, taper along pathways, and wrap around the house in irregular shapes.

Here’s how I handle it: break the area into rough rectangles and triangles. Measure each section separately, calculate the square footage of each one, and add them together. For curved beds, I use the closest rectangular approximation and add about 5% to account for the shape.

A few things people forget to measure:

• The strip between the driveway and the fence — it’s usually narrow but long, and those square feet add up fast.
• Tree rings — if you’re mulching around the base of trees, each one is a circle. Measure the diameter you want and work out the area.
• Slopes — a sloped bed has more surface area than its flat footprint suggests. If the slope is significant, add 10-15% to your area calculation.

The Square Footage Calculator handles the arithmetic for standard shapes. Plug in your measurements and it’ll give you the total area:

Write that number down. You’ll use it for everything that follows.

Mulch: how deep is deep enough?

Mulch does three jobs in your yard. It suppresses weeds, retains moisture in the soil, and insulates plant roots from temperature swings. But it only does those jobs if you spread it at the right depth.

Too thin (under 2 inches) and weeds push straight through within weeks. Too thick (over 4 inches) and you risk suffocating plant roots and creating a moisture trap that breeds fungus. The sweet spot for most bark and wood chip mulch is 2 to 3 inches. I go with 3 inches on beds that get full sun, because the top layer breaks down faster in direct heat, and 2 inches in shaded areas where decomposition is slower.

Here’s where people lose money: mulch is typically sold in bags (usually 2 cubic feet each) or in bulk by the cubic yard. Bags are convenient for small jobs, but they’re almost always more expensive per unit of volume. If you’re covering anything larger than about 100 square feet, bulk delivery will save you a significant amount. One cubic yard of mulch covers roughly 108 square feet at 3 inches deep — that’s about 13 to 14 bags’ worth.

Use the Mulch Calculator to work out exactly how much you need. Enter your area and desired depth, and it’ll give you the volume in cubic yards and the number of bags:

Ordering tip: add 5-10% to whatever the calculator tells you. Mulch settles after you spread it, and you’ll always have edges and corners that eat more material than the flat sections. I’d rather have a small pile left over than make another trip.

Gravel: driveways, paths, and drainage beds

Gravel is a different beast from mulch. It doesn’t decompose, it doesn’t float away in the rain (mostly), and it compacts over time into a firm surface. I use it for pathways, the strip alongside my garage, and a drainage bed at the back of the property where water used to pool after every storm.

Depth requirements vary by use:

• Decorative ground cover (around plants or along a fence line): 2 inches is enough.
• Walkways and garden paths: 3 to 4 inches gives a stable surface that doesn’t shift underfoot.
• Driveways and parking areas: you’re looking at 4 to 6 inches minimum, often with a compacted base layer underneath.
• Drainage beds: 4 to 6 inches, sometimes deeper depending on the volume of water you need to manage.

Gravel is heavier than mulch, which means delivery is essentially mandatory for anything beyond a small path. A cubic yard of gravel weighs roughly 1.2 to 1.5 tonnes depending on the type — you’re not hauling that in the back of a hatchback.

The type of gravel also affects coverage. Pea gravel (those small, rounded stones) packs tighter than angular crushed stone. Larger decorative river rock leaves more air gaps and covers less area per cubic yard at the same depth. If you’re using anything larger than 20mm stone, bump up your volume estimate by 10%.

The Gravel Calculator takes the guesswork out. Enter your dimensions and depth, and it gives you the volume and approximate weight:

Landscape fabric under gravel is non-negotiable. Lay a proper woven geotextile under any gravel area. Without it, the gravel slowly sinks into the soil and weeds push up from below. I’ve seen people skip the fabric to save a few dollars, and within two years they’re pulling the gravel out, laying fabric, and starting over. Do it once, do it right.

Putting together your materials list

Once you’ve got your area measured and your mulch and gravel volumes calculated, build a proper materials list before you place any orders. Here’s my standard checklist for a landscaping project:

1. Square footage of each zone (beds, paths, driveway strips)
2. Mulch volume in cubic yards, with the 5-10% buffer
3. Gravel volume in cubic yards, including the weight estimate for delivery planning
4. Landscape fabric — measure the same square footage as your gravel areas, plus 6 inches of overlap at every seam
5. Edging material — metal, plastic, or stone edging to keep mulch and gravel from migrating into the lawn
6. Fabric staples — one every 2 feet along seams and edges

Price everything out from at least two suppliers. Bulk landscape materials can vary wildly in cost between garden centres and dedicated aggregate yards. In my experience, the aggregate yard is usually 20-30% cheaper on gravel and roughly comparable on mulch.

Timing and delivery

Order your bulk materials mid-week if you can. Weekends are peak delivery time for every landscaping supplier, and you’ll often wait longer or pay a premium for Saturday delivery. Most suppliers will dump the material on your driveway or at the kerb — make sure you have a wheelbarrow, a good rake, and a few hours blocked out for spreading.

For mulch, early spring and late autumn are the best times to lay it down. Spring mulching locks in soil moisture before summer heat arrives. Autumn mulching insulates roots heading into winter. Avoid mulching in the middle of a hot, dry spell — the fresh layer acts like insulation and can actually trap heat against the soil surface.

Gravel is less timing-sensitive, but avoid laying it on saturated ground. If the base is soggy, the gravel will sink unevenly and you’ll spend the next year trying to level it out.

The key takeaway from every landscaping job I’ve done — from my bungalow’s front beds to a full backyard drainage overhaul — is the same lesson that applies to every renovation project: measure twice, calculate once, and order with a small buffer. It’s always cheaper to return a leftover bag of mulch than to make an emergency run for more.