Paving

Sub-base calculator

Measure your area, enter the depth you are using, and work out the sub-base volume before you buy.

01Tell us what you can measure

Add your measurements, then check the steps before you buy.

Units

Step 1 · Your area

Measure length × width. Choose “I already know the total volume” if you have a reliable total.

How would you like to start?

Not sure what to measure? See the measurement diagram

Area01

Area name optionalHow do you know this area?

Length mWidth m

Step 2 · Depth you're using

Use the depth already given in your plan, product guidance or advice. Calculator.Shop does not recommend a depth.

Depth you're using Depth unit

02Your volume estimate

Your volume estimate will appear here.

No product details needed for this result.

What this does not cover: Quantity estimate only from the area, depth and optional product values you provide. It does not choose a sub-base product or depth, or assess ground, drainage, falls, excavation, compaction, suitability, load capacity, patio or driveway design, foundations, Building Regulations or installation.

Measuring tips

What to measure

Measure each rectangular area by length and width. Add another only when it belongs in this estimate. If you already have a reliable measured area, use the direct-area option instead.

Measure the finished surface or dimensions used by this tool. Keep a note of the values you enter.

Worked example

See it in practice

4 m × 3 m = 12 m². At 50 mm (0.05 m), 12 m² × 0.05 m = 0.6 m³.

Keep a noteUse values from your own plan, product guidance or supplier information.

Quick answers

Useful to know

How much sub-base do I need?

Measure the area or enter a reliable measured area, then enter the depth you are already using. The calculator multiplies those values and gives the volume in m³ before any product conversion.

Can this tell me how many tonnes I need?

Only when you enter a tonnes-per-cubic-metre figure or supplier density for the specific product you chose. Density varies, so Calculator.Shop never assumes one.

Does this tell me which sub-base or depth to use?

No. If your plan or chosen product calls it MOT Type 1, this tool estimates quantity from the measurements and product figure you enter; it does not decide whether that material is suitable. Ground conditions, drainage, falls, compaction, patio or driveway design and installation need separate project-specific checks.

Method and checks

How this estimate is put together.

Calculation checked

Last checked 20 October 2026 · review again by 20 October 2027. The method version is available in the detail below.

The calculation steps and rounding are shown and have been checked. Before buying, check the coverage, pack size or other product detail you entered.

Keep in mind: sub-base quantity estimate only; not ground, drainage, material, depth or installation design. This remains a planning estimate, not a design or approval.

Details that can vary: No universal sub-base density, tonnes conversion, allowance, product, depth or layer build-up is supplied.

Check the product details: A product-unit volume, stated product coverage, supplier density or tonnes-per-volume figure you choose to enter. Calculator.Shop does not choose or supply these figures.

See sources, values you can change and method history

Sources for this method

Calculating the area and the perimeterMathplanet / Mattecentrum · mathematical definition · Public reference, accessed 17 October 2026Supports: Rectangle area (length × width) where a Calculator.Shop tool asks for a measured section. Pack, roll or board coverage and any extra allowance are values the visitor enters.
VolumeWolfram MathWorld · mathematical definition · Public reference, accessed 17 October 2026Supports: Cuboid and cylinder volume derivations using common linear units.

Values you can change

The areas or volume you enter, the depth you are already using and any allowance you choose.

What we check

The stated calculation steps, rounding and limits of this estimate.

When we check it again

Before the area, depth, allowance or product-conversion method changes; Before a density, tonnes or product value is presented as anything other than visitor supplied; When the stated ground, drainage, depth or installation safety boundary changes.

Method history

v1.0 · 2026-10-20First Sub-base Calculator method: neutral geometry first; product conversion only from visitor or supplier values.

See how we verify calculations