How to Calculate Sand, Gravel, and Aggregates
Whether you're laying a paver patio, filling a sandbox, or creating a gravel driveway, accurately calculating the amount of material you need is the first step to a successful project. Ordering too little means frustrating delays, while ordering too much leads to wasted money and leftover material. This guide explains the simple formulas used to determine both the volume and weight of the aggregate you need.
Step 1: Calculate the Volume
The fundamental calculation for any rectangular or square project is for volume. The formula is straightforward:
Volume = Length × Width × Depth (or Height)
The most critical part of this step is ensuring all your measurements are in the same unit before you multiply them. For example, if your length and width are in feet, but your depth is in inches, you must convert the inches to feet (by dividing by 12) before calculating the volume in cubic feet. Our calculator handles these conversions automatically to prevent errors.
Step 2: Convert to Cubic Yards
While you might calculate the volume in cubic feet or cubic meters, bulk materials like sand, gravel, and topsoil are almost always sold by the cubic yard in the United States. To convert your volume into cubic yards, use the following conversions:
- From Cubic Feet: 1 cubic yard = 27 cubic feet. Divide your total cubic feet by 27.
- From Cubic Inches: 1 cubic yard = 46,656 cubic inches. Divide your total cubic inches by 46,656.
Step 3: Calculate the Required Weight
Sometimes you need to know the weight of the material, especially for shipping or structural load considerations. To find the weight, you need to know the material's bulk density, which is how much a certain volume of it weighs. The formula is:
Weight = Volume × Density
Density can vary significantly between materials and even based on moisture content. Here are some common approximate densities (always check with your supplier for precise figures):
- Dry Sand: ~95 lbs/ft³ (1520 kg/m³)
- Wet Sand: ~120 lbs/ft³ (1920 kg/m³)
- Gravel: ~105 lbs/ft³ (1680 kg/m³)
- Topsoil: ~75 lbs/ft³ (1200 kg/m³)
For circular areas, such as a base for a fire pit, you would first need to find the area using the formula for a circle (πr²), which you can do with our circle calculator, and then multiply by the depth to get the volume.