Gravel Calculator

A gravel calculator estimates how much gravel, crushed stone (kapchi / khadi), or river-pebble you need for driveways, paving sub-bases, drainage, or landscaping. Gravel is heavy — one cubic metre of standard 20mm crushed-stone aggregate weighs ~1.68 tonnes (1,680 kg) — so getting accurate quantities upfront saves on tractor-trolley over-orders or short-pours. Indian construction uses tonnes (1 tonne = 1,000 kg ≈ 2,205 lbs); imperial mode shows US short-tons.

This tool is built for homeowners laying a driveway or compound path, masons and contractors quoting a job, and DIY landscapers filling a planter bed or drainage trench. Instead of guessing, you enter three measurements — length, width, and depth — and instantly get the volume in cubic metres, the weight in tonnes, and the number of 50 kg bags. That lets you call your supplier with a firm figure rather than ordering "two trolleys and hoping".

The Formula: Volume First, Then Weight

Calculating gravel is a two-step process. Step 1 — find the volume. Multiply the length by the width to get the surface area, then multiply by the depth to get the volume. The only trick is keeping units consistent: in metric mode depth is entered in centimetres, so it is divided by 100 to convert to metres. The formula is Volume (m³) = Length (m) × Width (m) × (Depth cm ÷ 100). Step 2 — convert volume to weight. Multiply the volume by the density of the material. This calculator uses 1.68 tonnes per cubic metre, the typical density of 20mm crushed-stone aggregate sold across Indian markets. So Weight (tonnes) = Volume (m³) × 1.68. Pea gravel and river stone are a little lighter at roughly 1.5 t/m³, so if you are buying decorative pebble your real tonnage will be slightly lower than the crushed-stone estimate.

Worked Example: A Typical Indian Driveway

Suppose you are gravelling the approach to a row house. The patch measures 6 m long × 3 m wide, and you want a 10 cm compacted layer for car traffic. First, the area is 6 × 3 = 18 m². Next, the volume is 18 × (10 ÷ 100) = 18 × 0.10 = 1.8 m³. Finally, the weight is 1.8 × 1.68 = 3.024 tonnes, which rounds to about 3 tonnes. In bag terms that is 3,024 kg ÷ 50 = 61 bags of 50 kg. Most suppliers sell loose gravel by the tractor-trolley (roughly 2.5–3 m³ each in many regions), so you would order a single trolley and a top-up, not two full loads. Knowing the number in advance is what stops you paying for a second trolley you do not need.

Practical Tips

Always order 5–10% extra to cover settling, uneven sub-grade, and spreading losses — gravel compacts once vehicles run over it, so a layer that looks right when loose will sink. For driveways, build in two layers: a coarser 40mm base for load-bearing and a finer 20mm top for a clean finish, and compact each layer with a plate compactor or roller. Lay a geotextile fabric under decorative gravel to stop weeds and keep stone from sinking into the soil. When you get quotes, confirm whether the price is per tonne or per trolley, and whether cartage (delivery) is included — in many Indian towns the transport cost rivals the material cost for small orders.

Common Mistakes to Avoid

The single most common error is mixing up depth units — entering 10 (meaning 10 cm) but treating it as 10 m, which inflates the order a hundredfold. Always confirm depth is in centimetres in metric mode. The second mistake is ordering by volume but paying by weight (or vice versa) without converting — a supplier quoting "per tonne" needs your tonnage figure, not your cubic-metre figure. Third, people forget that gravel is sold loose and settles: skipping the 5–10% buffer leaves you a few bags short on the final stretch, and a second delivery for a small shortfall is rarely economical. Finally, do not assume every stone weighs the same — basalt, granite, and limestone differ slightly, and very fine grit or sand-heavy mixes pack denser than clean 20mm aggregate.

Recommended Depths by Application

Pathways and walkways: 5–8 cm of gravel over a compacted base. Driveways: 10–15 cm of gravel (often in two layers — a coarser 40mm base and finer 20mm top). Drainage applications: depth varies by engineering. Decorative landscaping: 5–8 cm is typically enough for ground cover. RCC PCC bedding uses 10 cm of 40mm aggregate as per IS 456.

Types of Gravel (Indian market)

20mm crushed stone (kapchi): the most common — used in concrete, sub-base, and driveways. 40mm aggregate: for PCC and heavy base courses. 10mm grit:for fine concrete and plasterwork. River pebbles / cobble: decorative landscaping and around water bodies. Density varies slightly by stone type (basalt, granite, limestone); this calculator uses an average of 1.68 t/m³ for crushed stone.