Gravel Calculator
Cubic yards, tonnes, and number of bags of gravel for a given area and depth
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What this calculator computes
The gravel calculator estimates the volume and weight of crushed stone, pea gravel, drainage rock, or any other loose aggregate needed to fill a rectangular area to a specified depth. Inputs are the area dimensions (length and width in feet or metres), the desired depth (typically 2–4 inches for driveways, 3–6 inches for paths, 1–2 inches for landscaping), and the bulk density of the chosen aggregate (around 1.5 t/m³ for crushed limestone, 1.4 t/m³ for pea gravel, 1.7 t/m³ for granite chippings). The calculator returns the volume in cubic yards, cubic metres, and cubic feet, and the weight in tonnes and US tons so the result can be cross-referenced against bulk-supply quotes (which tend to be by the cubic yard in the US and by the tonne in the UK and EU). It also estimates the number of bags needed if the gravel is sold in bagged units, using a default 50 lb (US) or 25 kg (UK) bag size adjustable through the bag-size input. Bulk delivery economics typically favour ordering 1.5–2× the calculated volume on driveway and pathway projects to absorb settling, edge spillage, and the inevitable re-spreading required after the first rain compacts the surface; this calculator returns the geometric volume only and the user should add their own waste factor on top. For drainage applications (French drains, soakaway pits) order 1.2× the calculated volume to allow for the void-fraction loss when the rock is washed of fines and packed into the trench.
Calculator
The formula
Formula
volume = length × width × depth weight = volume × density
Worked example
When to use this calculator
Use this calculator before ordering bulk aggregate from a quarry or builders' merchant for driveways, garden paths, French drains, soakaways, retaining-wall backfill, sub-base layers under patios and sheds, and decorative-stone landscaping. The calculator returns the geometric volume; for any project add a waste-and-settlement margin of 10–25% depending on the application. Driveways and paths benefit from the higher end of that margin (gravel settles 1–2 cm in the first month under traffic); decorative top-dressing benefits from the lower end. The calculator does not account for irregular shapes — for crescent driveways, oval pads, or terraced gardens, divide the area into rectangles and sum the volumes. Bulk-supply pricing economics typically reward orders of 5+ tonnes through a flat delivery charge, so it is often cheaper to order slightly more than needed and use the surplus for edging or smaller secondary projects than to order the exact figure and pay multiple delivery fees later.
Common input mistakes
- Confusing depth in inches with depth in feet. A 3-inch depth is 0.25 ft, not 3 ft — entering the inches figure directly into a feet-denominated calculation overstates the volume by a factor of 12. Always convert depth to the same length unit as the area dimensions before multiplying.
- Ignoring the bulk-density variation between gravel types. Pea gravel is around 1.4 t/m³, crushed limestone around 1.6 t/m³, granite chippings around 1.7 t/m³, and coarse sand around 1.5 t/m³. Using a generic "1.5" for all aggregates can produce a 15–20% error on the tonnage estimate, which matters when ordering by weight.
Frequently asked questions
How much gravel do I need for a driveway?
For a typical residential driveway, calculate length × width × depth (in consistent units) and add 15–20% for settlement and edge spillage. A 30 × 12 ft drive at 3 inches deep is 3.33 yd³ before settlement; ordering 4 yd³ is a sensible round-up. For new driveways being built up from bare ground, also include a 100–150 mm sub-base layer of MOT type 1 or DOT type 1, which is a separate calculation under the gravel topcoat.
What depth of gravel should I use?
Driveways need 50–100 mm (2–4 inches) of gravel over a compacted sub-base for vehicle traffic; pathways and patios need 50–75 mm (2–3 inches); decorative landscaping and mulch over weed membrane need 25–50 mm (1–2 inches). Drainage trenches use the depth of the trench itself (often 300–600 mm) filled with washed clean stone. Below 50 mm depth, gravel migrates under foot traffic and exposes the substrate.
How much does a tonne of gravel cover?
One tonne of typical crushed gravel covers about 10–11 m² at 50 mm depth, or 5–6 m² at 100 mm depth. The exact coverage depends on bulk density: pea gravel (lighter) covers a larger area per tonne than granite chippings (heavier). For US tons (2000 lb, slightly less than a metric tonne) the coverage is 9% lower for the same volume.
Should I order in cubic yards, cubic metres, or tonnes?
US suppliers typically sell by the cubic yard or US ton; UK and EU suppliers typically sell by the tonne or 1-tonne bulk bag. Both volume and weight units are equally valid; the conversion depends on the bulk density of the specific aggregate being purchased. Always confirm which unit your supplier quotes in and convert accordingly — a "ton" in the US is 2000 lb (907 kg), distinct from a UK long ton (2240 lb, 1016 kg) or a metric tonne (1000 kg).
How much waste should I plan for?
Add 10–15% for tidy rectangular projects, 15–20% for driveways and high-traffic paths to absorb settlement, and 20–25% for irregular shapes or projects where edge spillage is hard to recover. Drainage applications typically need only 10% extra because the rock is contained in the trench. For projects below 1 yd³ the percentage matters less than the practical minimum delivery quantity, which is often a 1-tonne bulk bag.