Driveway Calculator

Reviewed, sourced guidance

Driveway calculator: area and sub-base quantity

Published Reviewed 3 min read

Direct answer

Driveway area is the sum of separate, non-overlapping measured rectangles. A 6 m by 3 m driveway measures 18 square metres; at 150 mm depth, its base sub-base volume is 2.70 cubic metres before any order allowance. Tonnage is only calculated when you enter the aggregate supplier's density.

Split the measured driveway into separate rectangles that do not overlap. The calculator adds their areas, applies one shared depth, and shows optional tonnes from a density you provide.

Driveway area and sub-base estimate

Add non-overlapping areas at one depth. Tonnage needs supplier density; the planning prompt applies only in England.

    Method and limitations

    Model version: 2026-09-25-v6

    • Separate rectangles are added at one shared depth. Areas must not overlap; this calculator cannot detect overlap or confirm a site drawing.
    • Material volume uses the combined measured area and the explicit order allowance entered above.
    • No universal order allowance or separate compaction factor is assumed.
    • Tonnage is omitted unless you supply the selected aggregate's density.
    • The planning prompt compares measured area, before the allowance, with England's guidance for hard surfacing between the wall forming the dwellinghouse's principal elevation and a highway. It is not a planning decision.

    Key takeaways

    • Add as many measured rectangle areas as needed, then enter an order allowance and shared depth.
    • Supplier guidance differs; the calculator does not choose a universal allowance.
    • Sub-base volume uses the entered allowance and depth; tonnage needs an entered material density.
    • The 5 square metre prompt uses measured area and applies to the cited England guidance for land between the dwellinghouse's principal elevation and a highway.
    • The calculator never returns a price.

    How the calculation works

    Convert the measurements to metres first. Depth in millimetres is divided by 1000, so 150 mm becomes 0.15 m.

    Multiply each rectangle length by width and add the plan areas. Keep the rectangles separate and non-overlapping. Enter an order allowance for the material quantity, then multiply by shared sub-base depth for volume.

    Supplier guidance is not uniform: Materials Market advises at least 10 per cent extra for its MOT Type 1 product, while Armstrongs suggests around 5 to 10 per cent in its guide. These examples are not a universal specification, so the calculator requires your supplier or job-specific figure.

    • 6 m x 3 m gives 18 square metres.
    • For an irregular outline, divide it into any number of non-overlapping rectangles before entering an allowance.
    • At 0 per cent allowance, the 18 square metre example remains 18 square metres.
    • 18 square metres at 150 mm deep is 2.70 cubic metres before any allowance.
    • Tonnage is not shown until you enter a density from the chosen supplier.

    Sources for this section: Materials Market MOT Type 1 product guidance (observed 2026-09-24)Armstrongs Group MOT Type 1 guide (published 2026-04-23; observed 2026-09-24)

    Why the threshold note appears

    The calculator compares measured surface area, before the order allowance, with the 5 square metre threshold for hard surfacing on land between a wall forming the dwellinghouse's principal elevation and a highway.

    The flag is a prompt to check, not a statement that permission is required. The rule turns on the surface and on where the water goes.

    • The guidance describes permeable surfacing or directing water to a lawn or border within the property.
    • The flag is only an England prompt and does not decide whether permission is required.
    • The threshold uses measured surface area, not the extra material allowance.
    • The location test is land between a wall forming the dwellinghouse's principal elevation and a highway, not any paved area colloquially called a front garden.
    • The threshold also counts hard surfacing replaced over 5 square metres at that location.

    Sources for this section: GOV.UK, Guidance on the permeable surfacing of front gardens (page updated 2021-11-12; text copyright 2009; observed 2026-09-25)Legislation.gov.uk, Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2 Part 1 Class F (observed 2026-09-25)

    Reading the result

    The area tells you how much surface material is needed and what you are paying a contractor to cover.

    The volume-to-weight conversion depends on the density figure and product unit supplied. Confirm product, delivery unit and site access with the supplier.

    • Order surface material by area, allowing for cutting and pattern.
    • Use the supplier's quoted unit and confirm where the material can be delivered or tipped.
    • Confirm the sub-base depth rather than assuming one.

    Next steps

    1. Confirm the sub-base depth before ordering material.
    2. For a front garden in England, check the surface and drainage against the planning guidance.

    Sources

    Before you get quotes