FREE CONCRETE QUANTITY GUIDE

Calculate concrete volume for a specified base

Concrete volume is length × width × depth, with every dimension in metres. Measure the base, use its specified depth, keep any ordering allowance visible and confirm the final order with the supplier. The calculation estimates quantity; it does not design the base or choose the concrete mix.

1. Record the dimensions and specification

Sketch the footprint and label the measured internal dimensions of the space to be filled. Record the source of the required depth and any changes in thickness. Separate openings, thickened edges and other distinct parts instead of hiding them in one average.

Use the area calculator for rectangles or the irregular area calculator to split a more complex plan. Keep structural, ground, drainage and reinforcement decisions with the responsible designer or specialist.

2. Convert millimetres to metres

Divide a depth in millimetres by 1,000 before multiplying. For example, 100 mm is 0.1 m, not 1 m. Use the concrete calculator for base volume in m³, or the general volume calculator for another measured layer.

Worked example: a rectangular base

A base measuring 3 m by 2 m, at an illustrative specified depth of 100 mm, requires 3 × 2 × 0.1 = 0.60 m³ before an allowance. If the agreed ordering allowance is 10%, the planning figure becomes 0.66 m³. These dimensions, depth and allowance demonstrate arithmetic only; they are not a recommended base specification.

For two separate sections, calculate each volume and add the results. Check that shared or overlapping areas have not been counted twice. Do not round each input prematurely; apply the supplier’s order increment after reconciling the total.

3. Keep ordering units clear

Ready-mixed concrete is normally ordered by volume. A bag count for a particular premixed product needs that product’s stated yield: divide the required volume by the volume produced by one bag, using the same units, then round up. One cubic metre is 1,000 litres.

This volume calculator is not a brand-specific bag-yield calculator or a cement, sand and aggregate mix designer. Do not substitute a generic bag count, dry-material density or mix ratio for the chosen supplier’s instructions.

4. Check before placing the order

• Confirm footprint, specified thickness and any separately measured details.
• Record one allowance and whether it is already included.
• Confirm mix designation, intended use and any specialist requirements with the responsible person.
• Agree minimum order, rounding, delivery access, unloading and timing with the supplier.
• Plan the agreed placement, protection and safe handling arrangements before delivery.

Related free planning tools

The free concrete base planner helps organise the wider job. Use the excavation calculator for material to remove and the MOT Type 1 calculator for a separately specified sub-base. Browse all free calculators and measurement and planning guides for other projects.

The optional Concrete Base Project Pack provides printable checks and records; its product page lists the contents and price. This free guide remains available without purchase.

Planning guidance only. Follow the project specification and product instructions. Arithmetic does not establish ground suitability, structural adequacy or a safe method of work.