MOT Type 1 / Hardcore Calculator
Estimate MOT Type 1 sub-base volume, tonnes and bulk bags from the finished area and compacted depth.
How much MOT Type 1 do I need?
Enter the area length, width and intended compacted depth. The calculator works out the compacted volume, applies your allowance and converts that volume to an approximate weight using the density you selected.
Type 1 quantity formula
Volume = length × width × compacted depth
Approximate tonnes = volume × bulk density
Worked example: 8 m × 4 m at 100 mm
An 8 m by 4 m area at 100 mm compacted depth has a base volume of 3.20 m³. At the default planning density of 2.2 t/m³ that represents about 7.04 tonnes before any additional allowance is applied.
Compacted depth matters
Type 1 is normally placed and compacted rather than simply tipped loose. Enter the intended finished compacted depth into the calculator. The amount delivered can differ because loose material settles as it is spread and compacted, which is one reason supplier advice and sensible ordering allowance are important.
MOT Type 1, hardcore and sub-base
People often use the terms “Type 1”, “hardcore” and “sub-base” interchangeably when searching, but they are not always the same material. If a specification calls for a particular graded aggregate, order that specified product rather than relying only on the generic description.
Bulk bags versus loose tonnes
For small projects, merchants may sell Type 1 in bulk bags; larger quantities are often supplied loose by weight. Enter the actual bulk-bag weight shown by your supplier to get a more useful bag estimate.
Frequently asked questions
What depth should I enter?
Enter the compacted depth specified for your project. BuildCalcs deliberately does not choose the construction depth because requirements vary with the intended use and ground conditions.
Why is the loose delivered amount different from the compacted volume?
Aggregate occupies more space when loose and reduces in volume as it is compacted. The calculator starts from the required compacted volume and uses an allowance to help with planning.
How many bulk bags are in a tonne?
That depends on the advertised bag weight. For example, an 800 kg bag is 0.8 tonnes by weight. Enter your merchant's stated bag weight rather than assuming every bag is identical.
Can I use this for a driveway or patio sub-base?
Yes for quantity estimation, provided you enter the project dimensions and the compacted depth required by your chosen construction specification.