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Concrete Mixer Loads Converter — How Many Mixer Loads Do I Need?
Convert your total concrete volume in cubic metres into the number of mixer loads. Calculate cement bags, sand and aggregate for each batch and total mixing time.
Total volume of concrete needed
25kg bags per m³ of concrete (default 13 for C20 1:2:4)
Sharp sand volume per m³ concrete (default 0.45)
20mm aggregate volume per m³ concrete (default 0.9)
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How We Calculate This
This calculator converts a total concrete volume (in m³) into the number of individual mixer loads based on your mixer type and its usable output capacity.
Mixer Output Capacities
“Mini”, “half-bag” and “full-bag” are informal trade categories rather than standardised sizes, so the figures below are typical approximations — always check your own mixer’s rated mixing capacity.
- Mini Mixer (~90L drum): ~60 litres usable output per load
- Half-Bag Mixer (~130L drum): ~90 litres usable output per load (this matches a real Belle Minimix 130/150)
- Full-Bag Mixer (~180L drum): ~130 litres usable output per load (a larger site mixer, not a Belle Minimix)
- Barrow Mix (hand): ~40 litres per batch
Standard C20 Concrete Mix (1:2:4)
The materials are calculated using a standard C20 general purpose mix ratio of 1 part cement to 2 parts sharp sand to 4 parts coarse aggregate (20mm), by volume. Applying the usual dry-volume factor of ~1.54 to the wet concrete volume, each cubic metre requires approximately:
- ~320 kg of cement = about 13 bags of 25 kg (≈ 6.5 bags of 50 kg)
- 0.45 m³ of sharp sand (~720 kg at ~1,600 kg/m³)
- 0.9 m³ of 20mm aggregate (~1,575 kg at ~1,750 kg/m³)
Time Estimates
Mixing time per load varies by mixer — as a rough rule of thumb, allow ~8 minutes for a mini mixer, ~7 minutes for a half-bag, ~6 minutes for a full-bag and ~5 minutes for a barrow mix. These are approximate mixing-only times — total time per batch including loading, pouring and cleaning will be longer.
Frequently Asked Questions
It depends on your mixer size. A full-bag site mixer (~130L output) needs about 8 loads per m³. A half-bag mixer such as a Belle Minimix (~90L output) needs about 12 loads. A mini mixer (~60L output) needs about 17 loads, and hand mixing in a barrow (~40L) takes around 25 batches per m³.
For a standard C20 general purpose mix (1:2:4 ratio by volume) you need roughly 320 kg of cement per cubic metre, which is about 13 bags of 25 kg (or about 6.5 bags of 50 kg). This is derived by applying a dry-volume factor of about 1.54 to the wet concrete volume. It is a general-purpose mix suitable for foundations, paths and floor slabs. Stronger mixes (C25, C30) require more cement per m³.
The drum capacity is the total volume of the mixer drum, but you cannot fill it completely — you need room for the materials to tumble and mix properly. Usable output is typically about 65-70% of drum capacity. For example, a Belle Minimix has a 130-litre drum and a quoted maximum mixing capacity of about 90 litres of mixed concrete per load.
For small volumes (under 1 m³), site mixing is usually cheaper as ready-mix suppliers typically have a minimum order of 1-3 m³ with a premium for small loads. For volumes over 2-3 m³, ready-mix is often more cost-effective and saves significant labour time. The break-even point is typically around 1.5-2 m³.
Each mixer load takes approximately 5-8 minutes of mixing time, but the total time per batch including loading materials and placing concrete is closer to 10-15 minutes. For 1 m³ using a full-bag mixer, allow approximately 2-3 hours total including breaks. It is physically demanding work.
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Last updated: February 2026
Verified against UK standards · estimates only, confirm with your supplier.