Construction Math
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The UK's definitive groundworks calculator. Stop guessing your orders. DigFill calculates exact Type 1 MOT tonnages, manhole concrete displacement, and 16T grab lorry counts right from the trench.
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📏 Trench Builder
Full Screen ↗Muck Away
ⓘ~1 Grabs
~6.24m³ loose / ~6.24t
Material Order
ⓘ~7.35t
Displacement
0.245m³
1. Trench Geometry
2. Layer Build-Up (Free Version)
🔒 Top Fill (Auto-Depth)
0.00mMain Fill
Pipes
No pipes. Pure fill.
Materials Breakdown
10/20mm Pea Shingle
Compacted • 4.800m³ net space
~7.35t
~5.05m³ order (loose)
Save to Site Log (Pro)
⭕ Manhole Logic
Full Screen ↗Net Muck Away
~1 Grabs
~7.80m³ loose / ~7.80t
Import Materials
~4.20t
Displacement
1.831m³
1. Pit Geometry & Volume
Solid Excavation Volume
Raw cubic space in the ground
6.000m³
2. Physical Structure
Concrete Chamber
✓ Fits wellCover & Neck
Auto Brickwork Neck
Calculated gap to surface
0.30m
3. Layer Build-Up
Surface Fill
Main Surround
Auto DepthBase Bedding
Materials Breakdown
Type 1 MOT
Compacted • 1.250m³ net space
Surface Fill
~2.75t
~1.50m³ order (loose)
Pea Shingle
Compacted • 0.850m³ net space
Base Bedding
~1.45t
~0.90m³ order (loose)
Why Generic Volume Calculators Destroy Margins
In the ground, it's cubic metres. On the invoice, it's tonnes. If you fail to account for structural displacement and soil bulking factors, you pay the price.
The Displacement Trap
Standard volume calculators ignore the massive volume taken up by drainage pipes and thick concrete manhole rings. DigFill automatically subtracts this structure from your aggregate order.
The Muck-Away Mess
You forget that stiff clay bulks by up to 30% once it leaves the trench. Suddenly you have three surplus piles of spoil, no grab lorries on schedule, and a blocked site.
The Type 1 Over-Order
You order too much MOT Type 1 because you used a flat cubic-to-tonne conversion without factoring in the specific depth profiles. Now you're paying to haul surplus material away.
"If the aggregate truck is half-empty, you've wasted money. If the trench is half-empty, you've wasted a day."
Groundworks FAQ
Common Construction Calculations
How do you calculate Type 1 MOT tonnage?
To calculate your Type 1 MOT order, multiply your site's Length × Width × Depth to find the volume in cubic metres. Then, multiply that volume by the compacted density of Type 1 MOT (roughly 2.2 tonnes per cubic metre) and add 20% to account for physical compaction with a wacker plate. DigFill's material calculator automates this entirely.
How many tonnes fit in a standard UK grab lorry?
A standard 8-wheel grab lorry has a maximum legal payload of 16 tonnes. However, when calculating muck away volume, you must use the specific soil "swell factor." Solid clay expands by up to 30% when excavated, meaning a 10m³ solid trench will generate over 13m³ of loose spoil.
Why should I deduct pipe displacement?
Large drainage lines consume massive amounts of trench space. The formula is: Volume = π × (Pipe OD / 2)² × Length. Failing to subtract this volume from your aggregate order means you will buy tonnes of expensive pea shingle you physically cannot fit into the hole.
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