Aggregate & Ballast Calculator
Calculate volume, weight, and bag counts for all construction aggregates - sub-base, concrete mixes, drainage, and fill.
Density:
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Extra material to allow for compaction. MOT Type 1: 15-20%; loose fill: 10-15%.
5-10% recommended for cutting and uneven ground.
Areas
Area / element name
Length (m)
Width (m)
Job Costing (optional)
UK Market PricesFills in the material cost fields with current UK market prices. You can review and edit each price before applying.
Results
Total Area
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m²
Net Volume
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m²
Volume (inc. comp. + waste)
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m²
Weight to order
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tonnes
Bags to order
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Area Breakdown
| Area / element | Dimensions | Area (m²) | Net vol (m²) | Adjusted (m²) | Weight (t) |
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Frequently Asked Questions
How much ballast do I need for concrete?
For a C20 mix (1:4 cement:ballast): approximately 1.2 tonnes of ballast per m³ of finished concrete. For C25 (1:3): approximately 1.1 tonnes per m³. As a rule of thumb, one bulk bag of ballast (~850 kg) plus 6 cement bags yields around 0.7 m³ of concrete.
What is the difference between ballast, sharp sand and all-in aggregate?
Ballast (all-in aggregate) is a pre-blended mix of gravel and sharp sand - add only cement to make concrete. Sharp sand is the fine angular sand component used alone in concrete batching or as block paving bedding. Coarse aggregate (10-20 mm gravel) is the coarse component. Ballast is the simplest option for small on-site pours.
What aggregate should I use for a concrete mix?
General concrete (foundations, slabs, paths): all-in ballast at 4:1 (C20) or 3:1 (C25) ballast:cement. Site-batched mix: 1 cement : 2 sharp sand : 4 coarse aggregate by volume for C20 equivalent. For pointing and mortar (not concrete), use soft building sand rather than sharp sand or ballast.
How many bags of sharp sand and cement do I need per square metre of pointing?
For mortar pointing at 10 mm joint width: approximately 2 kg of mortar per m². A 25 kg bag of sharp sand with 2 kg of cement will point approximately 6-8 m². For kiln-dried sand used in dry-brushed block paving jointing, allow 3-5 kg per m² depending on joint width.
What is MOT Type 1 aggregate used for?
MOT Type 1 is a graded crushed aggregate (limestone, granite or recycled concrete) meeting Highways Agency Specification Series 800, used as a compactable sub-base for driveways, paths and hardstandings. Standard depth is 150 mm for residential driveways, increasing to 200-300 mm for heavier vehicles or poor ground conditions.
What waste allowance should I use for aggregate and ballast?
Add 5-10% waste for spillage and over-ordering. For MOT sub-base, increase calculated volume by 30% for compaction before ordering. Aggregate is sold in 25 kg bags, bulk bags (~850 kg) or loose by the tonne - loose loads are significantly more economical than bulk bags for larger quantities.