Gravel Calculator – How Much Gravel, Stone or Sand to Order
Whether you are building a driveway, laying a garden path, preparing a patio base or topping up a decorative bed, the hard part isn't spreading the stone. It's working out what to order. This gravel calculator turns the size of your area and the layers going into it into the numbers a supplier asks for: cubic yards or cubic metres, tons or tonnes, or a count of bags. It also shows how deep to spread each layer before compacting, how many trips it takes in your own pickup, and which way of buying is cheapest.
Volume vs weight: why suppliers quote both
Your project is measured in volume: length × width × depth. Quarries, though, often sell by weight because the loader bucket sits on a scale, while landscape yards tend to sell by the yard. To compare quotes you need both. The calculator works out the volume first, then multiplies by a bulk density to estimate the weight. A 20 × 10 ft bed at 3 in deep is 200 ft² × 0.25 ft = 50 ft³, or 1.85 yd³, which is about 2.6 US tons of pea gravel.
The tons-per-yard conversion, and why it varies
Most gravel and crushed stone weighs roughly 1.3–1.5 tons per cubic yard (about 1,550–1,780 kg/m³). The exact figure depends on the rock type, the size and grading of the stones, and how much water is in the pile. Dense-graded crusher run, with its fines filling the gaps, is heavier than clean single-size stone; topsoil is lighter; lava rock can weigh less than half as much. Rain adds weight too: wet sand and topsoil can be 10–20% heavier than dry.
Compaction: spread it loose, compact it down
The depth you enter is the finished, compacted depth. Road base and crusher run lose around 15–25% of their thickness under a plate compactor, so to end up with 4 in you spread about 4.8 in loose and buy about 20% more than the hole's volume. Clean #57 stone and pea gravel barely compact, and bedding sand under pavers is screeded rather than compacted. The layer cross-section shows each spread depth, and the dig depth is the sum of all the finished layers.
Typical depths by project
- Decorative bed: about 2 in of pea gravel over landscape fabric.
- Garden path or walkway: about 3 in of crushed stone, held in with edging.
- Patio or paver base: 4 in of compacted base plus 1 in of bedding sand.
- Gravel driveway: 4 in of crusher run with 2 in of clean stone on top, on firm, well-drained ground. Soft clay or heavy vehicles often need 8–12 in of base.
Clean stone vs crusher run
Clean stone (such as #57) has no fines, so water drains straight through it. That makes it good for drainage trenches and driveway surfaces, but it never locks into a firm, flat layer on its own. Crusher run (also called road base, "¾ in minus", 21A or MOT Type 1) includes stone dust that binds when compacted, giving the firm base you want under pavers, sheds and driveways. Many driveways use both: crusher run for strength, clean stone on top for grip and drainage.
Buying bulk vs bags
Bags are convenient for small jobs, but once you need more than about half a yard, bulk delivery is usually far cheaper per unit, even after the delivery fee. The calculator rounds every option up once, on each material's total, so you never end up a bag short. Enter the prices you are quoted and it marks the cheapest option for each material and adds up a job total.
Hauling it yourself safely
A cubic yard of gravel weighs well over a ton, more than many half-ton pickups are rated to carry. Check the payload on the sticker inside the driver's door and let the calculator split the load into trips. A bed that looks half full may already be at its limit.
Measuring an uneven area
Real ground is never perfectly flat. Measure the depth in several places and use the average, split an L-shaped or irregular area into rectangles that don't overlap, and add a waste allowance of 5–10% for spill, uneven ground and the stone left in the truck. Plan for landscape fabric under decorative gravel to keep weeds down, and edging along paths and beds to stop the stone from migrating into the lawn.