MOT Type 1 calculator
Convert area and compacted depth into tonnes using an editable bulk-density assumption.
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When to use it
Use after the required compacted sub-base depth and the selected material have been specified for the project.
How it works
Compacted volume = area × depth in metres. Estimated tonnes = compacted volume × density; the entered allowance is then applied.
Worked example
Assume a measured area of 20 m², a specified compacted depth of 100 mm, an illustrative compacted density of 2 t/m³ and a 10% allowance. 100 mm = 0.1 m; 20 × 0.1 = 2 m³ compacted volume; 2 × 2 = 4 tonnes; 4 × 1.10 = 4.4 tonnes. The density and allowance are assumptions, not universal Type 1 values, and the supplier may quote a different conversion or delivery increment.
Measurement guidance
Measured area, specified compacted depth, the supplier-confirmed density or conversion basis, and a visible project allowance.
Buying and specification checks
Depth, density, compaction method and allowance are project- and product-dependent. The result is an estimated mass, not a loose delivered volume or a structural specification; confirm the supplier’s sale unit and delivery increment.
Measure the compacted layer and plan the delivery
The calculator converts a specified layer into an estimated weight; it does not choose the build-up or describe the loose load that arrives.
- Measure the actual footprint and record the compacted depth from the selected project detail. Keep changes of depth as separate areas instead of averaging away an important variation.
- Confirm the exact Type 1 product, its suitability and the supplier’s density or volume-to-weight conversion. Record whether the figure describes loose material, compacted material or a quoted coverage basis.
- Plan the delivery format, vehicle access, unloading position, storage and route to the work. Check the supplier’s minimum load or ordering increment before turning the calculator result into an order.
- Place and compact to the specified layer thicknesses, equipment and method for the actual ground and loading. Recheck levels and completed compacted depth; do not invent a universal number of layers or passes.
Common mistakes
- Entering a loose tipped depth as the finished compacted depth
- Treating one density or compaction allowance as universal
- Ordering before checking delivery access, sale increments and the specified placement method
FREE TOOL AND PROJECT PACK
What the free calculator provides
The free calculator converts a measured area, specified compacted depth, supplier-confirmed density and visible allowance into an estimated tonnage. It does not choose the sub-base detail, convert a loose tipped load automatically or set the supplier’s delivery increment.
What the dedicated pack adds
The Patio Project Pack carries that quantity into the wider ordinary domestic pedestrian-patio plan and retained project record.
- Brief, site, measurement, level, water-route and paving-system decisions before ordering.
- Paving and bulk-material schedules, quote comparison, order gate, delivery and concealed-stage preparation checks.
- Laying, troubleshooting, completion, care and a retained patio project passport with product and build-up details.
19-page printable digital workbook (PDF). Immediate digital delivery with 90-day access; no subscription.
Practical FAQs
Is the loose delivered volume the same as the compacted volume?
No. The calculator starts from the finished compacted layer. Loose material contains more void space and changes volume during placing and compaction. Use the selected supplier’s conversion or quoted coverage rather than equating a tipped heap with the finished layer.
What density should I enter?
Use a density or conversion basis confirmed for the actual material and supply route. Aggregate source, grading, moisture and whether the figure is loose or compacted can change the relationship, so the example 2 t/m³ is illustrative only.
Does the result include the supplier’s delivery increment?
No. The calculator returns an estimated tonnage to three decimal places. Check whether the supplier sells by loose load, bulk bag, whole tonne or another increment, then round the order once using that rule and confirm vehicle access and unloading.
How deep should MOT Type 1 be and how should it be compacted?
The calculator does not choose either. Required compacted depth and placement method depend on ground, loading and the selected paving or construction detail. Follow that specification and the current product and equipment instructions; seek competent advice where the detail is uncertain.
Planning guidance, not a quotation or a substitute for project-specific design and competent advice.