Planning guide

How to calculate gravel for a driveway

The arithmetic is simple. The important choices are measuring each layer, using a realistic depth, and confirming how your supplier sells the material.

The short answer

Multiply length × width × depth

Use the same unit for every dimension. In metric, multiply length in metres by width in metres by depth in metres to get cubic metres. For US customary units, multiply length in feet by width in feet by depth in inches, then divide by 324 to get cubic yards.

Metric example

6 m × 3 m × 100 mm

1.80 m³ 6 × 3 × 0.10

US customary example

20 ft × 10 ft × 4 in

2.47 yd³ 20 × 10 × 4 ÷ 324

These are geometric volumes before any supplier-specific allowance. A calculator can help with the arithmetic, but it cannot choose the right driveway design for your soil, slope, drainage, traffic, or local requirements.

Step 1

Measure the area and each planned layer

Measure the length and width. For a rectangular driveway, measure the usable gravel area rather than the whole property frontage.
Split irregular shapes. Divide an L-shape or taper into rectangles, calculate each rectangle, and add the volumes.
Record the target depth for each layer. A base and a wearing layer are separate quantities; do not hide different materials inside one average depth.
Use an average depth when ground varies. Measure several representative points and ask the supplier or designer how to handle slopes, soft spots, excavation, and drainage.

Step 2

Do not treat one depth as a universal rule

Driveway build-ups vary with subgrade, climate, slope, vehicle use, aggregate grading, drainage, and local approvals. Use a project specification, local authority guidance, or a knowledgeable supplier to choose the target compacted depth before ordering.

As one local example—not a universal recommendation—the City of Santa Barbara’s permeable gravel driveway guidance lists a minimum of 6–8 inches of compacted aggregate for its specified driveway design and also considers slope, compaction, permeability, and the distance from the public right-of-way. Read the official Gravel Driveway Guidance before applying that example to a different place or project.

Step 3

Use the right unit conversion

Metric volume = length (m) × width (m) × depth (m)

US volume = length (ft) × width (ft) × depth (in) ÷ 324

The 324 comes from 27 cubic feet per cubic yard × 12 inches per foot.

Convert millimetres or centimetres to metres before multiplying. In the US formula, keep depth in inches; converting it to feet first and dividing the resulting cubic feet by 27 gives the same answer.

Step 4

Turn volume into an order estimate

Gravel may be sold by cubic metre, cubic yard, tonne, short ton, bulk bag, or another supplier-specific unit. Volume is the stable starting point. Do not convert it to weight using a generic density when your supplier can provide the product’s bulk density, moisture condition, and whether the quoted quantity is loose or compacted.

Ask which material grade and nominal size the quote covers.
Confirm whether the quoted depth is loose or compacted.
Ask how the supplier handles delivery minimums and rounding.
Keep any waste or uncertainty allowance visible in your notes.

Use the gravel calculator for a rectangular area, metric or US customary units, a visible waste allowance, and a nominal density assumption. Replace that assumption with supplier information before placing an order.

Before ordering

A compact driveway estimate checklist

Length, width, and the usable gravel boundaries are recorded.
Each layer has its own material and target depth.
Irregular areas and changing ground levels are accounted for.
Local drainage, slope, access, and approval requirements are checked.
The supplier has confirmed ordering units, density, and rounding.

This is a planning guide, not structural, drainage, engineering, or regulatory advice. See the shared calculation methodology for how Measure Materials handles units, assumptions, waste, and rounding.

Related tools