One of the first questions that comes up when planning a gravel driveway is how much material you actually need. Order too little and you’re making multiple trips or paying extra delivery fees. Order too much and you’ve got a pile of expensive stone sitting in your yard with nowhere to go.
The good news is that calculating gravel tonnage isn’t complicated once you know the formula. This guide walks you through the math step by step, with real examples based on typical driveway sizes here in North Georgia.
The Basic Formula
Calculating gravel needs comes down to figuring out the volume of material required and then converting that volume to weight. Here’s the formula broken into steps.
Step 1: Calculate Volume in Cubic Feet
Start with three measurements: length, width, and depth. All measurements need to be in the same unit for the math to work.
Length (feet) × Width (feet) × Depth (feet) = Cubic feet of gravel
For depth, you’ll need to convert inches to feet. Divide your depth in inches by 12. So a 4-inch layer becomes 0.33 feet, and a 6-inch layer becomes 0.5 feet.
Step 2: Convert to Cubic Yards
Gravel is typically sold by the cubic yard or by the ton. To convert cubic feet to cubic yards, divide by 27 (since there are 27 cubic feet in a cubic yard).
Cubic feet ÷ 27 = Cubic yards
Step 3: Convert to Tons
Most gravel weighs between 1.3 and 1.5 tons per cubic yard, depending on the type and moisture content. Crush and run tends toward the heavier end, while clean stone is a bit lighter. A safe average to use is 1.4 tons per cubic yard.
Cubic yards × 1.4 = Tons of gravel needed
Putting It All Together
Let’s say you’re building a driveway that’s 200 feet long, 12 feet wide, and you want a 4-inch layer of crush and run.
First, convert the depth: 4 inches ÷ 12 = 0.33 feet
Then calculate volume: 200 × 12 × 0.33 = 792 cubic feet
Convert to cubic yards: 792 ÷ 27 = 29.3 cubic yards
Convert to tons: 29.3 × 1.4 = 41 tons
For this driveway, you’d need about 41 tons of crush and run for a single 4-inch layer.
Calculating for Multiple Layers
A properly built gravel driveway has three layers: base, middle, and surface. Each layer uses different material at different thicknesses. You’ll need to run the calculation separately for each layer.
Example: Full Driveway Build
Using the same 200 × 12 foot driveway, here’s what a professional installation might require:
Base layer (4-inch clean stone): 200 × 12 × 0.33 = 792 cubic feet 792 ÷ 27 = 29.3 cubic yards 29.3 × 1.4 = 41 tons of 3-inch clean stone
Middle layer (3-inch stone): 200 × 12 × 0.25 = 600 cubic feet 600 ÷ 27 = 22.2 cubic yards 22.2 × 1.4 = 31 tons of 2-inch stone
Surface layer (3-inch crush and run): 200 × 12 × 0.25 = 600 cubic feet 600 ÷ 27 = 22.2 cubic yards 22.2 × 1.5 = 33 tons of crush and run (using 1.5 because crush and run packs heavier)
Total for all three layers: 41 + 31 + 33 = 105 tons
That’s a lot of rock. It’s also why professional driveway installation costs what it does.
Quick Reference for Common Sizes
Here are tonnage estimates for single 4-inch layers on typical driveway sizes. These assume a width of 12 feet.
100-foot driveway: about 21 tons 150-foot driveway: about 31 tons 200-foot driveway: about 41 tons 300-foot driveway: about 62 tons 500-foot driveway: about 103 tons
For 10-foot wide driveways, multiply these numbers by 0.83. For 14-foot wide driveways, multiply by 1.17.
Accounting for Compaction
Here’s something that trips people up. When you compact gravel, it loses volume. A 4-inch layer of loose stone might compact down to 3 inches or less. Professional contractors account for this by ordering 10 to 15 percent more material than the calculations suggest.
If your math says you need 40 tons, order 44 to 46 tons. You can always use the extra material to top off low spots or stockpile it for future repairs. Running short in the middle of a project is far more costly than having a little left over.
Material Weight Variations
Different types of gravel have different weights. Here are approximate weights per cubic yard for materials commonly used in Georgia:
Crush and run: 1.4 to 1.5 tons per cubic yard 57 stone (washed): 1.3 to 1.4 tons per cubic yard 3-inch clean stone: 1.3 tons per cubic yard Granite screenings: 1.4 tons per cubic yard Pea gravel: 1.3 tons per cubic yard
When in doubt, ask your supplier. They can tell you the weight of the specific material they carry, which makes your calculations more accurate.
Delivery Considerations
Most gravel suppliers deliver in tandem dump trucks that carry 15 to 22 tons per load, depending on the truck and local weight limits. Larger tri-axle trucks can haul up to 25 tons.
When you’re ordering 40 tons, that’s two or three truckloads. Delivery fees are typically charged per load, so minimizing the number of deliveries saves money. Some suppliers offer discounts on larger orders, making it cheaper per ton when you buy more.
If your driveway or property access is tight, make sure the supplier knows ahead of time. Some sites can only handle smaller trucks, which means more loads and higher delivery costs.
What About Top-Offs & Repairs?
Existing driveways that just need a refresh typically require 1 to 2 inches of new material. For a 200 × 12 foot driveway with a 2-inch top-off:
200 × 12 × 0.167 = 400 cubic feet 400 ÷ 27 = 14.8 cubic yards 14.8 × 1.4 = 21 tons
Plan to add this amount every 3 to 5 years for routine maintenance, depending on traffic and weather conditions in your area. Properties in the Dahlonega and North Georgia foothills may need more frequent top-offs due to the hilly terrain and heavy rain runoff.
Do the Math Before You Call
Running these calculations before you contact a supplier or contractor puts you in a better position to evaluate quotes. You’ll know roughly what you need, and you can ask informed questions about material recommendations and pricing.
Some contractors include material in their quotes while others bill it separately. Knowing your tonnage helps you compare apples to apples when reviewing estimates.
A few minutes with a calculator now saves confusion and overspending later. Measure your driveway, run the numbers, and you’ll know exactly what you’re working with before the first truck shows up.
