Gravel & Aggregate
How Much Gravel Do I Need?
Calculate gravel for any project: the volume formula, compaction and waste corrections, cubic-yards-to-tons conversion, and a coverage table by depth.
Gravel math is concrete math with two twists that catch people: the material shrinks when you compact it, and suppliers sell it by weight while you measure it by volume. Miss either conversion and your "exact" order comes up 20–30% short. Here's the complete method.
Step 1: Volume from geometry
For circles: area = πr². For irregular areas, split into rectangles and add. Measure depth as the finished, compacted layer you want.
Step 2: Correct for compaction
Crushed stone loses 10–20% of its loose volume under a plate compactor as particles interlock. If you want 4 compacted inches, you must place nearly 4.7 loose inches. Multiply geometric volume by 1.15 as a default; use 1.10 for clean single-size stone (it compacts less) and up to 1.20 for dense-graded base with fines.
Step 3: Add waste
Spreading, edge spill, and material left where the truck dumped it cost about 5%. Total correction: geometry × 1.15 × 1.05 ≈ geometry × 1.21.
Step 4: Convert to tons
| Material | Loose density | Tons per yd³ |
|---|---|---|
| Pea gravel | ~2,400 lb | 1.2 |
| Sand | ~2,600 lb | 1.3 |
| Crushed stone (3/4 in clean) | ~2,700 lb | 1.35 |
| Bank-run gravel | ~2,800 lb | 1.4 |
| Crusher run / dense base | ~2,900 lb | 1.45 |
Moisture adds 5–15% to these dry weights - after rain, the same yard of stone weighs noticeably more, which matters because you pay by the ton. Details in Cubic Yards of Gravel to Tons.
All four steps automated, with six material densities and truckload planning built in.
Open the Gravel CalculatorWorked example: 12 × 25 ft parking pad
- Target: 4 in compacted crusher run over fabric
- Geometry: 12 × 25 × 0.333 = 100 ft³ = 3.70 yd³
- Compaction ×1.15 and waste ×1.05: 4.47 yd³ loose
- Tons: 4.47 × 2,900 ÷ 2,000 = 6.5 tons
- Delivery: fits one tandem load
Coverage quick-reference
| Depth | 1 yd³ covers | 1 ton covers* | Typical use |
|---|---|---|---|
| 2 in | 162 ft² | ~100 ft² | Path topping, mulch alternative |
| 3 in | 108 ft² | ~65 ft² | Driveway surface course |
| 4 in | 81 ft² | ~50 ft² | Slab base, pad |
| 6 in | 54 ft² | ~33 ft² | Driveway base lift |
| 12 in | 27 ft² | ~17 ft² | Drain trench backfill |
*Crushed stone at 1.35 tons/yd³, before compaction allowance.
Common mistakes
Ordering finished volume. The compaction step is the one first-timers skip; it's why the driveway that "should have taken 12 tons" needed 14.
One density for all products. Pea gravel and crusher run differ by 20% per yard. Match the density to the actual product.
Guessing depth. Depth is the most powerful input - going from 3 to 4 inches raises the order 33%. Decide depth from the job (see the table), don't default to "a few inches."
No fabric on soft ground. On clay or wet subgrades, geotextile separation keeps stone from disappearing into the mud over the first two seasons - it can effectively halve long-term stone consumption on driveways.
When to call a professional
Gravel under structures, engineered fills, and road base under pavement is specified by gradation and compaction testing, not by rules of thumb. If an inspector will look at it or a building will sit on it, get the spec from the design documents first.
Frequently Asked Questions
How much gravel do I need for 100 square feet?
At 2 inches deep: 0.62 cubic yards (about 0.9 tons). At 4 inches: 1.23 cubic yards (about 1.8 tons). Add 15% if the layer will be compacted, plus 5% waste.
How many square feet does a ton of gravel cover?
Roughly 100 sq ft at 2 inches deep, 65 sq ft at 3 inches, and 50 sq ft at 4 inches, for typical crushed stone at 1.35 tons per cubic yard.
Should I buy gravel by the yard or by the ton?
Suppliers quote either, but delivery tickets are usually weighed in tons. Calculate volume first, convert using the material's density, and confirm the supplier's own conversion factor when comparing quotes.
Why did my gravel 'disappear' after compacting?
Compaction reduces loose volume by 10-20%. A 4-inch loose layer compacts to about 3.4 inches. Order the loose volume needed to achieve your target compacted depth - the calculator's 15% default handles this.
How deep should gravel be for different projects?
Paths: 2-3 inches over fabric. Slab base: 4 inches. Driveway: 8-12 inches total in layers. French drain: fills most of an 18-24 inch trench. Depth drives quantity more than any other input.