UK Trench Volume &
Muck Away Calculator
The ultimate drainage trench calculator. Instantly calculate exact Type 1 MOT tonnages, pea shingle bedding volumes, and 16-tonne grab lorry muck away requirements while automatically subtracting pipe OD displacement.
Drainage Trench Volume & Grab Lorry Estimator
- 1
Enter Trench Dimensions & Pipe OD
Input your trench length, width, and total depth. Enter the pipe diameter to trigger the displacement subtraction automatically.
- 2
Select Spoil Type for Muck Away
Choose your existing ground type (e.g., Clay, Topsoil, Hardcore) to calculate the specific loose-spoil swell factor for your grab lorries.
- 3
Build Your Aggregate Layers
Add 100mm/150mm bedding tracks and specify which layer contains the pipe. The calculator deducts reused spoil to give your net material supplier order.
Save to Your Digital Site Log
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Create a Free AccountMuck 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)
Why Use a Dedicated Trench Backfill Calculator?
Standard volume calculators ignore the realities of UK site engineering. DigFill accounts for soil swell, pipe displacement, and aggregate compaction.
Type 1 MOT & Pea Shingle Volume
Stop guessing your aggregate orders. Our pea shingle calculator isolates the 150mm bedding and surround layers, while determining the exact Type 1 MOT tonnage required for your final backfill, preventing expensive over-ordering.
UK Muck Away Calculator
Excavating native clay or topsoil creates a 20-30% volume expansion (the swell factor). Our muck away calculator translates solid trench cubic metres into loose spoil, giving you an exact 16T grab lorry capacity breakdown.
Pipe Displacement Formula
Large drainage pipes consume massive amounts of trench space. Our engine automatically applies the pipe displacement volume formula based on the Outside Diameter (OD), actively deducting the pipe's volume from your aggregate order.
Common Groundworks Calculations (FAQ)
How do you calculate trench backfill volume?
To calculate trench backfill volume, multiply the trench length by its width and depth to get the total cubic volume. Next, subtract the physical volume displaced by the drainage pipe. Finally, convert the remaining cubic metres into tonnes based on the aggregate's compacted density (e.g., Type 1 MOT requires approximately 2.2 tonnes per cubic metre).
How many tonnes does a 16t grab lorry hold?
A standard 8-wheel UK grab lorry has a maximum legal payload capacity of 16 tonnes (roughly 12-14 cubic metres of loose material). When calculating muck away logistics, you must account for the soil "swell factor." Solid clay expands by up to 30% once excavated, meaning you will need more grab lorry capacity than your solid trench dimensions suggest.
How do I calculate pipe displacement?
The pipe displacement formula is: Volume = π × (Pipe OD / 2)² × Length. It is crucial to use the Outside Diameter (OD), not the internal diameter, as the thickness of the pipe wall (especially on large concrete or twin-wall plastic pipes) displaces a significant amount of backfill aggregate.