Ordering and mixing
Ready-mix order quantity with waste
- where
- volume including waste (m³)
- calculated concrete volume (m³)
- waste allowance (%)
- volume to order (m³)
- order increment (m³)
Explain this equation
Turns a calculated concrete volume into a sensible ready-mix order.
Concrete is lost in uneven ground, spillage and what stays in the drum, so a waste percentage is added. Suppliers sell in steps, often a quarter of a cubic metre, so the result is rounded up to the next step.
Percentage uplift, then rounding up to a whole number of increments.
Sense check: 2.4 m³ with 5% waste is 2.52 m³, which orders as 2.75 m³ in 0.25 m³ steps.
Watch out: running short on a pour is far worse than having a little left over. Many plants have a minimum load, so very small pours may suit a volumetric truck.
Adds a waste allowance to your calculated volume and rounds up to the next whole order step, such as 0.25 m³.
Enter your values to see the result.
Good to know
Concrete suppliers commonly recommend adding 5–10% for spillage, uneven formation and over-dig; use the top of that range for trench fill and rough ground. The increment is whatever your supplier sells in: 0.25 m³ is common for small and volumetric loads, 0.5 m³ or 1 m³ for full trucks. Ask the supplier about part-load charges and minimum loads.
Common mistake
Ordering the exact calculated volume. Running short on a pour leaves a cold joint and a second delivery charge, which costs far more than a little spare concrete.
Limits
Allowances are rules of thumb, not a guarantee. Very uneven ground or soft spots can take far more.
Sources
- Heidelberg Materials (Hanson), Ready-mix concrete volume calculator FAQ (add 5–10% to the calculated volume for spillage and uneven surfaces)
- Tarmac, What are your minimum concrete mixes – delivered? (minimum 1 m³ standard ready-mix in most regions; check load sizes with sales)
- Carvers, Readymixed concrete C20 0.25 m³ (small loads sold in 0.25 m³ units)
Results are calculations from the published methods and figures shown, and depend on the data you enter. Follow BS 8500, BS EN 206, BS EN 752, Building Regulations Part H, manufacturers’ data and your engineer’s design. Structural concrete and foundations need a competent designer.