Patio Aggregate Calculator: How Much Gravel You Need

A patio aggregate calculator works out the volume of gravel, crushed stone, or sand needed to fill a patio base or surface. You enter the patio length, width, and the depth of the aggregate layer, and the calculator returns the volume in cubic yards and cubic feet. This tells you how much material to order, so you avoid both shortages and costly over-ordering.

Formula

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

Volume (ft³) = Length (ft) × Width (ft) × Depth (in) ÷ 12

Then it converts cubic feet to cubic yards by dividing by 27 (since 1 yard = 3 feet, so 1 yd³ = 27 ft³):

Volume (yd³) = Length (ft) × Width (ft) × Depth (in) ÷ 324

Where:

• Length – the longest side of the patio in feet (or meters, but then convert to feet first).
• Width – the shorter side in feet.
• Depth – the thickness of the aggregate layer in inches.
• 324 – the conversion factor: 27 (ft³ per yd³) × 12 (inches per foot).

Worked Example

Using the default values: length = 40 ft, width = 25 ft, depth = 3 in.

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

The calculator shows 9.26 yd³ (rounded to 2 decimals) and 250 ft³. That matches the formula exactly.

How to Use the Result

The result is the volume of aggregate you need to fill the space to the specified depth. In practice, you’ll order slightly more because:

• Aggregate compacts when tamped, so the final depth is less than the loose volume.
• Patio shapes are rarely perfect rectangles; irregular edges need extra.
• Suppliers sell in whole cubic yards or by ton, and you can’t order a fraction of a delivery.

For a 40×25 ft patio at 3 inches deep, you’d order about 10 cubic yards (rounding up from 9.26). If you’re buying by the ton, multiply cubic yards by the material’s density (typically 1.4 tons per cubic yard for crushed stone, but check with your supplier).

Choosing the Right Depth

The depth you need depends on what the aggregate is for:

• Patio base (under pavers): 4–6 inches of compacted crushed stone is common for a stable base.
• Loose gravel surface (walking area): 2–3 inches is usually enough.
• Under a shed or hot tub: 6–8 inches may be needed for load-bearing.

If you’re unsure, ask a local landscape supplier – they know the soil and frost conditions in your area. The calculator gives you the volume for any depth, so you can compare options.

Common Mistakes and How to Avoid Them

• Mixing units: Always use feet for length and width, and inches for depth. If you measure in meters, convert to feet first (1 m = 3.281 ft).
• Forgetting compaction: Loose aggregate settles by 10–20% when compacted. If you need a 4-inch compacted base, you may need to order 5 inches of loose material.
• Rounding too early: Don’t round the volume until the end. The calculator does this correctly.
• Ignoring waste: Add 5–10% for spillage, irregular shapes, and settling.

Limitations of the Calculator

This calculator assumes a perfectly rectangular area with uniform depth. Real patios have curves, slopes, and varying thickness. For complex shapes, break the area into rectangles and add the volumes, or use a more advanced method. Also, the calculator gives volume, not weight – the weight depends on the material’s density, which varies (e.g., crushed limestone is heavier than pea gravel). Check with your supplier for the specific weight per cubic yard.

Frequently Asked Questions

How many cubic feet are in a cubic yard?

There are 27 cubic feet in one cubic yard (3 ft × 3 ft × 3 ft). That’s why the calculator divides by 27 after converting to feet.

Should I order more than the calculator says?

Yes, it’s wise to order 5–10% extra to account for compaction, waste, and irregular edges. For the example above, 9.26 yd³ becomes about 10 yd³.

Can I use this for sand or soil?

Yes, the volume calculation works for any bulk material. Just note that the weight per cubic yard differs (sand is about 1.2 tons, soil about 1.1 tons).

What if my patio is not a rectangle?

Break it into rectangles, calculate each, and add the volumes. For a circle, use π × radius² × depth. The calculator only handles rectangles.

How do I convert cubic yards to tons?

Multiply the cubic yards by the material’s density in tons per cubic yard. For crushed stone, that’s often around 1.4, but check with your supplier.

What depth do I need for a paver patio?

Typically 4–6 inches of compacted base under the pavers, plus 1 inch of sand for leveling. This calculator can help with the base layer.

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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