Gravel Calculator: How Much Gravel Do I Need?

This gravel calculator tells you exactly how much gravel you need in cubic yards and cubic feet based on the length, width, and depth of the area you plan to fill. Enter your measurements in feet and inches, and you’ll get the volume of gravel required, which you can then use to order the right amount from a supplier. It works for driveways, paths, garden beds, and any other project where you need to spread a layer of crushed stone or pebbles.

Formula

The calculator uses the basic volume formula for a rectangular prism:

Volume (ft³) = Length (ft) × Width (ft) × Depth (ft)

Because depth is entered in inches, the formula first converts inches to feet by dividing by 12. Then, to get cubic yards (the standard unit for ordering gravel), it divides the cubic feet by 27 (since 1 yard = 3 feet, so 1 yd³ = 27 ft³). The combined formula is:

Volume (yd³) = (L × W × D/12) / 27 = L × W × D / 324

Where:

• L = length in feet
• W = width in feet
• D = depth in inches

The output gives you both cubic yards (the common unit for bulk orders) and cubic feet (useful for smaller projects or bagged gravel).

Worked Example

Let’s use the default values: a 40 ft long by 25 ft wide area, with a 3-inch depth of gravel.

1. Convert depth to feet: 3 in ÷ 12 = 0.25 ft
2. Calculate volume in cubic feet: 40 ft × 25 ft × 0.25 ft = 250 ft³
3. Convert to cubic yards: 250 ft³ ÷ 27 = 9.26 yd³

The calculator shows 9.26 yd³ (rounded to 2 decimals) and 250 ft³. That means you need about 9.26 cubic yards of gravel to cover a 40×25 ft area at 3 inches deep.

Why Use a Gravel Calculator?

Ordering gravel without knowing the volume is a recipe for either running short mid-project or ending up with a huge pile you didn’t need. A gravel calculator helps you:

• Order the right amount – bulk gravel is sold by the cubic yard, so knowing your volume prevents over- or under-ordering.
• Compare costs – once you have the volume, you can multiply by the price per yard from a local supplier.
• Plan for delivery – knowing the volume helps you estimate how many trips or how large a delivery truck you need.

It’s especially useful for landscaping projects like driveways, walkways, French drains, or base layers for patios.

How to Choose the Right Gravel Depth

The depth you need depends on the purpose of the gravel. Here are common guidelines (but always check with a local supplier or contractor for site-specific advice):

• Walkways and paths: 2–3 inches of gravel is usually enough.
• Driveways (parking area): 4–6 inches, sometimes more if the subgrade is soft or the driveway sees heavy vehicles.
• Base layer for pavers or slabs: 4–6 inches of compacted gravel is typical.
• French drains or trench: 6–12 inches, depending on the pipe size and drainage needs.

If you’re unsure, it’s better to err on the side of slightly deeper, but remember that more depth means more gravel, more cost, and more labor.

Common Mistakes and How to Avoid Them

Even with a calculator, mistakes happen. Here are the most common ones:

• Mixing units – always measure in feet for length/width and inches for depth. If you measure in meters, convert to feet first (1 m = 3.28084 ft).
• Forgetting compaction – gravel compacts when driven or walked on, so the final depth may be less than what you spread. Many contractors order 10–15% extra to account for compaction and settling.
• Assuming 1 ton = 1 cubic yard – gravel density varies by type; a cubic yard of gravel typically weighs between 2,400 and 2,900 lbs (1.2–1.45 tons). Always ask your supplier for the weight per yard, not just the volume.
• Rounding down – when ordering bulk gravel, always round up to the next full yard, because suppliers usually deliver in whole yards.

How to Measure an Irregular Area

Not every project is a perfect rectangle. For L-shaped or irregular areas, break the area into rectangles, calculate each one, and add them together. For circular areas, use the formula Ï€ × r² (where r is the radius in feet) to get the area, then multiply by the depth. The calculator only handles rectangles, so for circles you’ll need to do that part manually.

If your area is curved or has a slope, it’s best to measure at several points and use an average depth. On slopes, the actual volume can be slightly different because the gravel settles differently on an incline.

Buying Gravel: Bulk vs. Bags

Gravel is sold either in bulk (by the cubic yard) or in bags (typically 0.5 ft³ or 1 ft³ bags, or 50-lb bags). Here’s how to decide:

• Bulk (by the yard) – best for large projects (more than a few cubic yards). It’s cheaper per yard and delivered by truck.
• Bags – convenient for small projects or if you don’t have a way to receive bulk delivery. One cubic yard equals 27 ft³, so if you buy 1 ft³ bags, you need 27 bags per yard.

For a 40×25 ft area at 3 inches deep (9.26 yd³), you would need about 250 ft³ of bagged gravel, which is 250 one-cubic-foot bags. That’s a lot of bags, so bulk delivery is usually the practical choice for anything beyond a small path.

Frequently Asked Questions

How many square feet does a yard of gravel cover?

It depends on the depth. One cubic yard (27 ft³) spread 3 inches deep (0.25 ft) covers 108 square feet (27 ÷ 0.25 = 108). At 2 inches deep, it covers 162 square feet; at 4 inches, it covers 81 square feet.

How do I convert gravel from cubic yards to tons?

Multiply the volume in cubic yards by the density of the gravel in tons per cubic yard. Most gravel weighs about 1.4 tons per yard, but it varies from 1.2 to 1.7 depending on the type. Ask your supplier for the exact figure.

Can I use this calculator for pea gravel or crushed stone?

Yes, the volume calculation is the same for any type of gravel, pebble, or crushed stone. The only difference is weight per cubic yard, which you’d need to know for ordering by ton.

What if my area is not a rectangle?

Break it into rectangles, calculate each with the calculator, and add the results. For circles, use the formula π × r² × depth in feet, then divide by 27 to get cubic yards.

Should I order extra gravel?

Yes, it’s wise to order 10–15% more than the calculated volume to account for compaction, settling, and uneven ground. Many people also want a little extra for future touch-ups.

Final Tips

Before you order, measure twice and use this calculator to get the volume. Then contact a local gravel supplier to confirm the weight per yard and delivery options. Always round up to the nearest half or whole yard, and consider having the gravel delivered on a day when you have help to spread it – gravel is heavy and hard to move by hand.

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in l | Lawn length | ft | 40 | 0 | 100000
in w | Lawn width | ft | 25 | 0 | 100000
in d | Depth | in | 3 | 0 | 120
out yd | Volume | yd³ | l * w * d / 324 | 2
out ft3 | Volume | ft³ | l * w * d / 12 | 1