How Much Gravel Do I Need?
The exact method contractors use to estimate gravel — turn your area and depth into cubic yards and tons, with a worked driveway example, a quick tonnage table, and the formula behind every number.
To find how much gravel you need, multiply length × width × depth (all in feet) to get cubic feet, divide by 27 for cubic yards, add about 10% for compaction, then multiply by the stone's density — roughly 1.4 tons per cubic yard for crushed stone. A 20 ft × 10 ft driveway at 4 inches of #57 stone works out to about 2.72 cubic yards, or 3.8 tons, so you would order 4 tons.
Buying gravel is deceptively easy to get wrong. Order too little and the delivery truck leaves before your driveway is finished; order too much and you are paying to haul away a pile of leftover stone. The fix is a five-minute calculation that any contractor can do in their head, and this guide walks through every step of it. By the end you will be able to turn an area and a depth into a confident number of tons — and know why the number is what it is.
If you would rather skip the arithmetic, the gravel calculator runs all of this for you and adds a compaction factor automatically. But understanding the method makes it easy to sanity-check any quote a supplier gives you.
The four numbers that decide everything
Every gravel estimate comes down to four inputs:
- Area — the square footage you are covering.
- Depth — how thick the gravel layer will be.
- Waste / compaction — extra material to allow for settling and tamping.
- Density — how heavy the chosen stone is, which converts volume into tons.
Get those four right and the rest is multiplication and division.
Step 1: Find the area
For a rectangular driveway or pad, area is simply length × width. For a round area like a fire-pit base, use π × (radius)². Keep everything in feet:
Rectangular area = length × width Circular area = π × (diameter ÷ 2)²
A 20 ft × 10 ft driveway is 20 × 10 = 200 square feet. A round fire-pit base 10 ft across is π × 5² ≈ 78.5 square feet.
Step 2: Convert to volume, then cubic yards
Gravel is a volume, so multiply the area by the depth — but depth is usually given in inches, so convert it to feet first (divide inches by 12). Then divide by 27, because there are 27 cubic feet in a cubic yard:
Cubic feet = area × (depth in inches ÷ 12) Cubic yards = cubic feet ÷ 27
Four inches is 4 ÷ 12 = 0.333 ft. Our driveway is 200 × 0.333 = 66.67 cubic feet, which is 66.67 ÷ 27 = 2.47 cubic yards.
Step 3: Add a waste and compaction factor
Loose gravel shrinks when it is spread and tamped down — anywhere from 10% to 20% of its delivered volume. For a simple spread layer, add about 10%; for a base course you will mechanically compact, use 15–20%. Our example uses the standard 10%:
2.47 × 1.10 ≈ 2.72 cubic yards
Step 4: Convert cubic yards to tons
Suppliers sell gravel by weight, so multiply your cubic yards by the stone’s density. Crushed #57 stone runs about 1.40 tons per cubic yard:
Tons = cubic yards (with waste) × density
2.72 × 1.40 ≈ 3.8 tons
Because gravel is sold in whole tons, you would order 4 tons. That single number is the whole point of the exercise — and it matches exactly what the gravel calculator returns for the same inputs.
Worked example: a two-car parking pad
Say you are graveling a 24 ft × 24 ft two-car pad at 4 inches of #57 stone:
- Area:
24 × 24 = 576 sq ft - Volume:
576 × 0.333 = 192 cubic feet = 7.11 cubic yards - With 10% waste:
7.11 × 1.10 ≈ 7.82 cubic yards - Tons:
7.82 × 1.40 ≈ 10.95 tons→ order 11 tons
Quick reference: tons of #57 gravel by area and depth
These assume #57 crushed stone (1.40 tons per cubic yard) with a 10% compaction factor — the calculator’s default. Use them as a starting point, then confirm your exact figure with the gravel calculator.
| Area | 2 in | 3 in | 4 in | 6 in |
|---|---|---|---|---|
| 100 sq ft | 0.95 t | 1.43 t | 1.90 t | 2.85 t |
| 200 sq ft | 1.90 t | 2.85 t | 3.80 t | 5.70 t |
| 400 sq ft | 3.80 t | 5.70 t | 7.60 t | 11.41 t |
| 600 sq ft | 5.70 t | 8.56 t | 11.41 t | 17.11 t |
Notice that doubling the depth doubles the tonnage, and doubling the area does too — gravel scales linearly, which makes these numbers easy to interpolate for any project in between.
Get the depth right
Depth is the input people most often underestimate. As a rule of thumb: decorative ground cover needs about 2 inches, walkways and paths about 3 inches, and a driveway about 4 inches per layer. Real driveways are usually built in two layers — a compacted crusher-run base plus a finer top course — so a full-depth driveway can easily need 6–8 inches total, doubling the tonnage in the table above. Our companion guide, Gravel Coverage & Depth Chart, lays out recommended depths for every project type and shows how far a ton stretches at each one.
Pick the right stone for the job
Density is not the only thing that changes with material — so does whether the gravel will lock together or stay loose. Clean #57 stone drains freely but never firms up; #411 crusher run packs into a solid base but holds water. Choosing the wrong one is the most common gravel mistake there is. Gravel Types & Sizes breaks down #57, #411, pea gravel, river rock and sand so you buy the stone that actually suits your project.
Don’t forget the delivery minimum
Bulk gravel almost always has a minimum load — often 1 to 3 tons — plus a flat delivery fee. For a tiny job, a few bags from the hardware store can work out cheaper once haulage is added. For anything driveway-sized, bulk delivery wins on price every time. Either way, once you know your tonnage from the gravel calculator, you can compare bagged versus bulk pricing with real numbers instead of guessing.