ganak.appSub Base Calculator
Calculate sub base tonnage, bulk bags, and cost for MOT Type 1, 2, 3, and crusher run. Supports patios, driveways, and paths in metric or imperial units.
Dimensions
Material
Cost Estimation
Add material and labour cost
Total Material Required
MOT Type 1 · 10% compaction included
Weight
3.30tonnes
Area & Volume
Calculated from 5 m × 3 m × 100 mm
Material Quantity
MOT Type 1 at 2 t/m³ density
What Is a Sub Base Calculator?
Understanding sub base materials and how to calculate quantities
A Sub Base Calculator helps you determine exactly how much aggregate material you need for your landscaping or construction project. Enter your area dimensions, choose your material, and the calculator instantly computes the weight in tonnes, bulk bags required, and estimated cost.
5 Materials
MOT Type 1, 2, 3
6F4/6F5 & Crusher Run
Dual Units
Metric
and Imperial
Free
No sign-up
Unlimited calculations
Common applications: Patio and paving sub-bases, driveway foundations, artificial grass base layers, block paving, shed bases, paths and walkways, and road construction. A properly compacted sub-base prevents sinking, cracking, and water pooling.
How Is Sub Base Material Calculated?
The formulas behind material estimation
The calculation uses four simple steps: find your area, multiply by depth and material density, then apply a compaction factor for real-world accuracy.
Volume
Volume (m³) = Length × Width × (Depth mm ÷ 1000)
Multiply your area dimensions to get the total volume in cubic metres. For imperial, the calculator converts feet to metres automatically.
Weight
Weight (tonnes) = Volume × Material Density (t/m³)
Each material has a different bulk density. MOT Type 1 uses 2.0 t/m³. The calculator applies the correct density for your selected material.
Compaction
Adjusted Weight = Weight × (1 + Waste% ÷ 100)
Sub base compacts by 10–25% when rolled. A 10% waste factor is standard for most residential projects. Adjust the slider for your specific needs.
Bulk Bags
Bulk Bags = Ceil(Adjusted Weight ÷ 0.85)
Standard bulk bags hold approximately 850 kg. Always round up — it's better to have a little extra than to run short mid-project.
Worked Example: 5 m × 3 m Patio at 100 mm Depth
- Area = 5 × 3 = 15 m²
- Volume = 15 × (100 ÷ 1000) = 1.5 m³
- Weight = 1.5 × 2.0 (MOT Type 1) = 3.0 tonnes
- With 10% compaction: 3.0 × 1.10 = 3.3 tonnes
- Bulk bags needed: Ceil(3.3 ÷ 0.85) = 4 bags
Material Density Reference
Industry-standard bulk densities for common sub base materials
Bulk density varies by material type, moisture content, and compaction level. The values below are industry averages used for estimation. Actual density can vary by ±10%.
| Material | Loose | Comp. |
|---|---|---|
| MOT Type 1 | 1.9 | 2.2 |
| MOT Type 2 | 1.8 | 2.1 |
| MOT Type 3 | 1.7 | 2.0 |
| 6F4 / 6F5 | 2.0 | 2.3 |
| Crusher Run | 1.9 | 2.2 |
Important: This calculator uses an average between loose and compacted density. Always order 5–10% extra material to account for variations in density, uneven ground, and material lost during spreading.
Common Mistakes to Avoid
Get your quantities right the first time
Too shallow a depth
A sub base that is too thin will not provide adequate support. For patios use at least 75 mm; for driveways use at least 150 mm. Cutting corners on depth leads to sinking and cracked surfaces.
Forgetting compaction allowance
Sub base material compacts by 10–25% when rolled or tamped. Always add a waste factor. Ordering the exact calculated volume means you will run short after compaction.
Wrong material type
MOT Type 3 is free-draining but has less structural strength than Type 1. Use Type 1 for load-bearing applications, Type 3 for drainage areas, and 6F4/6F5 for heavy-duty construction. Using the wrong material leads to premature failure.
Mixing up units
Mixing millimetres with metres is the most common mistake. If your length and width are in metres but depth is in millimetres, divide depth by 1000. Our calculator handles this automatically whether you use metric or imperial units.
Which Sub Base Material Should You Use?
A quick guide to choosing the right material for your project
MOT Type 1
The most common sub base material. A mixture of crushed rock, concrete, and brick (40 mm down to dust). Ideal for patios, driveways, paths, and general hard landscaping. Compacts to a hard, stable base.
MOT Type 2
Finer grade than Type 1 with smaller aggregate size. Used where a smoother finish is required or where thinner layers are being laid. Common for block paving and finer grading work.
MOT Type 3
Open-graded, free-draining material with fewer fines. Used for permeable paving, French drains, and Sustainable Urban Drainage Systems (SUDS). Allows water to drain through while providing structural support.
6F4 / 6F5
Heavy-duty specification materials from the Highway Works series. 6F4 is a coarse graded granular sub-base; 6F5 is a finer variant. Used for road construction, heavy industrial flooring, and large-scale civil engineering projects.
About This Calculation
How the estimates are derived and what assumptions are made
The weight is calculated as Volume × Material Density. Density values are industry averages; actual weight may vary based on moisture content, compaction, and specific material source.
A compaction/waste factor (adjustable from 5–25%) is applied to account for settlement during compaction and material lost during spreading. One bulk bag is assumed to contain approximately 850 kg of material.
Important: These estimates are for planning purposes only. Always confirm quantities with your supplier and consider ordering an extra 5–10% for irregular areas, uneven ground, or unexpected variations in material density.
Frequently Asked Questions
Common questions about sub base materials, depths, and calculations
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Last updated May 22, 2026