Gravel Calculator by Square Footage

A gravel calculator by square footage works out the volume and weight of gravel you need for a project. You enter the area’s length and width in feet, the desired gravel depth in inches, and the gravel density (usually about 1.68 tons per cubic yard), and it returns the cubic feet, cubic yards, and estimated tons required. This lets you order the right amount without overpaying or running short.

Formula

The calculator uses two straightforward formulas:

• Volume (cubic feet) = Length (ft) × Width (ft) × Depth (ft), where Depth in feet = Depth in inches ÷ 12.
• Weight (tons) = Volume (ft³) × Density (lb/ft³) ÷ 2000 (since a ton is 2000 pounds).

If you prefer cubic yards, divide the cubic feet by 27 (because 1 cubic yard = 27 cubic feet). The density of gravel varies by type and moisture, but a typical value is 105 lb/ft³ (about 1.4 tons per cubic yard). For reference, dry gravel is usually 100–110 lb/ft³, while wet gravel can reach 120–130 lb/ft³.

Worked Example

Using the default values from the calculator: length = 20 ft, width = 10 ft, depth = 4 in, density = 105 lb/ft³.

1. Convert depth to feet: 4 in ÷ 12 = 0.333 ft.
2. Volume in cubic feet: 20 × 10 × 0.333 = 66.6 ft³.
3. Cubic yards: 66.6 ÷ 27 = 2.47 yd³.
4. Weight in tons: 66.6 × 105 ÷ 2000 = 3.50 tons (rounded to two decimals).

So for a 20×10 ft area at 4 inches deep, you need about 2.47 cubic yards or 3.50 tons of gravel (assuming 105 lb/ft³ density). Most suppliers sell gravel by the cubic yard or ton, so this matches what you would order.

Why Depth Matters More Than You Think

The depth you choose dramatically changes the volume. A 1-inch difference on a 100 ft² area changes the volume by about 0.31 cubic yards (roughly 0.42 tons). Common depths:

• 2 inches – light walkways or decorative mulch replacement.
• 3–4 inches – typical for driveways and patios.
• 6 inches or more – heavy vehicle traffic or base layers.

If you are unsure, 4 inches is a safe default for most residential projects. For driveways that see large trucks, go to 6 inches. Remember that gravel compacts over time, so you might need a bit more than the calculated volume if you want the final surface to sit at a certain height.

How to Measure Your Area

Accurate measurements are key. Use a tape measure or a laser distance measurer for straight edges. For irregular shapes, break the area into rectangles and triangles:

• For a rectangle: length × width.
• For a triangle: (base × height) ÷ 2.
• For a circle: Ï€ × radius².

Add the volumes of each section together. If your project is a long driveway with curves, you can approximate it as a series of rectangles and add a 5–10% buffer. Always measure in feet for length and width, and inches for depth, to keep the calculator inputs consistent.

Understanding Gravel Density and Weight

Gravel density is not a fixed number. It depends on the type of stone and how much moisture it holds. Here are approximate densities for common gravels (in lb/ft³):

• Pea gravel – 95–105
• Crushed stone (limestone) – 100–110
• Bank run gravel – 100–120
• Wet gravel – 120–130

If you don’t know the exact density, use 105 lb/ft³ as a general estimate. When ordering, suppliers often quote by the ton, so knowing the approximate weight helps you compare prices. For example, 2.47 cubic yards at 105 lb/ft³ is about 3.50 tons; at 120 lb/ft³ it would be 4.00 tons. That difference matters for cost and for how many trips you need.

Common Mistakes and How to Avoid Them

Even with a calculator, people make errors. Watch out for:

• Mixing units – Always convert depth to feet before multiplying. A common error is to use inches directly, which gives a volume 12 times too large.
• Forgetting compaction – Gravel settles. If you need a 4-inch final depth, you might need to order 5–6 inches worth to account for settling, especially under heavy use.
• Ignoring the sub-base – For driveways, you often need a base layer of larger stone (e.g., #3 or #4 crushed stone) under the top layer. That base layer adds volume and weight.
• Rounding too early – Keep at least two decimals in your calculations until the end. Rounding the cubic feet to a whole number early can shift the tonnage by 0.2 tons or more.

Also, remember that the calculator gives the volume of gravel in place. When you order, you might need to account for the fact that gravel is sold by the cubic yard, but the truck’s load is measured loose. Loose gravel can have a different density than compacted gravel, but for most projects the difference is small.

Limits of the Formula

This calculator is a planning tool, not a guarantee. It assumes a flat, uniform area and a consistent gravel depth. Real-world factors like slopes, curves, and irregular ground will change your needs. Also, the density you enter is an estimate; the actual weight per cubic foot of the gravel you receive can vary by up to 10% or more. For large projects, it’s wise to order 5–10% extra to account for these variations and for spillage during placement. If you are building a road or a structure that requires engineered fill, consult a civil engineer or your local supplier for specific recommendations.

Frequently Asked Questions

How many square feet does a ton of gravel cover?
At a 2-inch depth, a ton of gravel (2000 lb) covers about 100–120 square feet, depending on density. At 4 inches, it covers about 50–60 square feet. Use the calculator to get an exact figure for your depth.

Do I need to add extra gravel for compaction?
Yes, most projects benefit from adding 5–10% more gravel than the calculated volume. This accounts for settling and for the fact that the ground may not be perfectly level. For driveways, consider 10% extra.

What is the difference between gravel and crushed stone?
Gravel is naturally rounded, often found in riverbeds, while crushed stone is mechanically broken, giving it angular edges. Crushed stone locks together better for driveways, while pea gravel is more decorative and shifts more easily.

Can I use this calculator for other materials like sand or soil?
Yes, the formula works for any bulk material. Just change the density to match the material (e.g., sand ~100–130 lb/ft³, topsoil ~80–110 lb/ft³). The volume calculation stays the same.

How do I measure an irregularly shaped area?
Break the area into rectangles, triangles, and circles, calculate each separately, and sum the volumes. For a curved driveway, approximate with rectangles and add 5–10% extra to cover the gaps.

Should I order by cubic yard or by ton?
Most suppliers sell by the cubic yard, but some quote by the ton. Use the calculator to get both numbers. If you know the density, you can convert: cubic yards × density (lb/ft³) × 0.0006 ≈ tons (since 1 yd³ = 27 ft³ and 2000 lb/ton).

Related

• Driveway Square Footage Calculator: How To Measure
• Drop Ceiling Tile Calculator: How Many Tiles You Need
• Gravel Driveway Calculator: How Much You Need

in len | Length | ft | 20 | 0
in wid | Width | ft | 10 | 0
in dep | Depth | in | 4 | 0
in dens | Density | lb/ft³ | 105 | 0
out cubic_ft | Cubic feet | ft³ | len * wid * (dep / 12) | 2
out cubic_yd | Cubic yards | yd³ | cubic_ft / 27 | 2
out tons | Estimated tons | tons | cubic_ft * dens / 2000 | 2