Gravel Calculator
About Gravel Calculation
This Gravel Calculator converts site dimensions and layer thickness into volume in m³ and weight in tonnes. Enter length × width, a ready area, a circle by diameter, or an irregular shape, then set thickness after compaction or provide a loose thickness with a compaction factor. Choose fraction (grain size), origin, washing, moisture and allowance to get area, volume, mass (kg and t), coverage per 1 t and total cost.
The tool works entirely in metric units (cm, m, m², m³, kg, t) and is suitable for pea gravel, crushed rock and stone chippings used in landscaping, bases and drainage.
Tips and Tricks
- Input methods: pick Length × width, Area (m²), Circle by diameter (cm), or Irregular shape (4 sides). The calculator averages the opposite sides for irregular areas and shows the computed area in m².
- Thickness and compaction: if your thickness is specified before compaction, switch to “Before compaction” and set the factor. Aggregates commonly compact by 1.10-1.30×. The result uses thickness after compaction.
- Density presets: fraction, origin and washing set a realistic bulk density. Rounded river gravel is slightly lighter, crushed quarry stone slightly heavier; washed material is ~5% lighter than unwashed because of fewer fines. Moisture adds mass (0%, +2% or +4%) but not volume.
- Allowance (waste): for edging cuts, settlement and delivery variation, people often add 5-15%. Increase it for irregular borders or hand spreading.
- Handy coverage rules of thumb (≈1.5 t/m³ bulk density): 3 cm ≈ 22.2 m²/t; 5 cm ≈ 13.3 m²/t; 8 cm ≈ 8.3 m²/t; 10 cm ≈ 6.7 m²/t. Your coverage will update automatically from the density and thickness you set.
- Prices: choose whether your supplier quotes per tonne or per m³—enter one number and the tool calculates total cost accordingly.
| Fraction (mm) | Common use |
|---|---|
| 2/8, 4/8 | Paths, decorative beds, light drainage (often called pea gravel). |
| 8/16, 16/32, 20/40 | Universal subbases, drainage, concrete work. |
| 32/64, 40/70 | Drainage layers, bank and slope protection. |
| 0/22, 0/32, 0/45, 0/63 | With fines; compacts very well for bedding and road bases. |
Grain-size notation follows European aggregate grading; fractions correspond to EN 13242 ranges. For concrete mixes see EN 12620 guidance used locally.
Formulas used (metric):
volume (m³) = area (m²) × thickness after compaction (m)mass (t) = volume (m³) × bulk density (t/m³)coverage (m² per 1 t) = 1 ÷ (density (t/m³) × thickness (m))
FAQs
How do I figure out how much gravel I need?
Select the site shape, enter dimensions in centimetres or area in m², set the layer thickness and how it's specified (before/after compaction), then pick fraction and properties. The gravel estimator instantly returns volume in m³, weight in tonnes and total cost.
Which fraction should I choose for pea gravel, crushed rock or stone chippings?
For decorative paths use 2/8-4/8 mm (pea gravel). For general bases and drainage, 8/16-20/40 mm crushed rock is common. Mixtures with fines such as 0/32 compact best for subbases; coarse 32/64 and larger are for high-drainage or protection layers.
How many tonnes are in 1 m³ of gravel?
Depending on grain size and fines, bulk density typically ranges from about 1.35 to 1.65 t/m³. Finer mixes with fines are heavier; rounded washed gravel is lighter. The calculator sets density from your selected fraction, origin and washing so the tonnage is computed automatically.
Should I enter thickness before or after compaction?
If your project spec states a compacted layer (common for bases), keep “After compaction”. If you only know the loose thickness, switch to “Before compaction” and enter a factor, usually 1.10-1.30, to account for the reduction after compaction.
Can I use this rock and stone calculator to estimate cost?
Yes. Choose whether your quote is per tonne or per m³ and fill in the price field. The tool multiplies by the calculated mass or volume and adds your allowance to show the total.