From area to tons: how the math works
Gravel is measured by volume but usually sold by weight, so the calculator does both steps. First the volume — area times depth, with the depth converted to the same unit as the area:
Volume = length × width × depth (US: ft × ft × in ÷ 12 → ft³, then ÷ 27 → yd³)
Then the conversion to weight using the material's bulk density: a cubic yard of crushed stone weighs about 2,700 lb, so multiplying volume by density and dividing by 2,000 gives US tons (metric: volume × tonnes/m³). That's the number you actually tell the quarry or landscape yard when you order.
Why the allowance is not optional here
Two things quietly inflate every gravel order. Loose stone settles — a fresh 3-inch layer becomes 2½ inches after weather and foot traffic do their work. And base material is meant to be compacted: running a plate compactor over road base reduces its volume by 10–20% by design, which means you buy loose volume to end up with less compacted volume. The default 10% covers ordinary settling and spillage; push it to 15–20% when you're building a compacted driveway or patio base, where the shrinkage is intentional.
Bulk or bags?
The bag row is there mostly as a reality check. A modest 10 × 20 ft parking strip at 3 inches deep is about 2 cubic yards with allowance — roughly 110 bags of 50 lb gravel. Nobody wants to be the person loading cart number six at the store. As a rule of thumb, bags make sense below about half a cubic yard (a path repair, a drainage strip behind a downspout); anything larger is a bulk order, where a delivered cubic yard typically costs a third to half of the same volume in bags.
Frequently asked questions
Do I need landscape fabric under gravel?
For decorative gravel over soil, fabric keeps stone from sinking into mud and slows weeds — usually worth it. Under a compacted driveway base, practice varies; geotextile helps on soft subgrades but codes and soil conditions decide.
What size gravel for a driveway?
A common build-up: larger crushed stone (e.g. ¾–1½ inch) as the compacted base, topped with a smaller angular stone (⅜–¾ inch) as the surface. Rounded pea gravel rolls under tires, so it's better for paths and beds than for driveways.
How many wheelbarrow loads is a cubic yard?
A typical 6 cubic-foot wheelbarrow filled realistically (not heaped) moves about 4–5 ft³ of gravel, so a cubic yard is roughly 6–7 loads — and at ~2,700 lb total, plan your route before the truck dumps the pile.
Does the calculator handle irregular areas?
Split the space into rectangles and circles, run each, and add the tonnages. For gentle curves, using the average width of the strip as the rectangle width gets you well within the waste allowance.
Building something on top? Size the pour with the concrete calculator, and finish the job with the paint calculator.