Gravel is sold by volume or weight, but the layer you install changes as it is spread and compacted. Decide whether your depth is loose or finished, then use a supplier density that describes the same condition.
Measure the finished layer
Sketch the area and split it into rectangles. Measure the target compacted depth at several locations; a single edge measurement can miss a crown or a low spot. Convert inches to feet or centimetres to metres before multiplying.
Separate geometry from density
Length × width × depth gives volume. Weight is volume multiplied by bulk density. Density varies with aggregate type, grading, moisture, and whether the material is loose or compacted, so an editable input is more honest than one fixed number.
Ask the quarry or bag label which density and delivery unit they use. Do not substitute a wet density for a loose bulk estimate without explaining the difference.
Compaction and allowance
A finished 4-inch layer may require more loose material before compaction. The exact factor depends on the aggregate and equipment. Use the calculator’s allowance as a planning input, then validate it with the supplier or installer rather than presenting it as a code value.
Driveways and paths behave differently
A vehicle driveway may use more than one aggregate layer, while a decorative path may be a shallow single layer. Calculate each layer separately when products or depths differ; do not average unlike materials into one density.
Worked examples
Driveway base
- Use 24 × 12 ft and a 6 in finished depth (0.5 ft).
- Volume is 144 ft³, or 5.33 yd³.
- Apply the selected allowance, then multiply by the supplier density.
Result: The weight is an estimate until the quarry confirms its bulk-density basis.
Garden path
- Use 30 × 3 ft at 2 in (0.167 ft).
- Volume is about 15 ft³, or 0.56 yd³.
- Compare bulk delivery with the minimum practical bag order.
Result: A small path can be governed by packaging and delivery minimums rather than the theoretical volume alone.