Pipe bedding is the granular material placed directly around the pipe — below it (bedding layer), beside it (haunching) and above it to 300mm (initial backfill). Trench fill is everything above the embedment zone up to the finished surface. Bedding is typically imported crushed rock or DGB20. Trench fill is usually compacted native material or road base.

For a full hydraulic estimate including a complete materials schedule, contact SNZ. We include bedding and trench fill quantities in every estimate we produce.

AS/NZS 3500 requires 300mm minimum cover from the top of the pipe to the finished surface in unpaved areas, and 500mm in paved areas subject to traffic loading. This calculator applies both requirements automatically — if you enter a depth that does not meet the minimum, the depth adjusts instantly and shows you the corrected value.

SNZ applies AS/NZS 3500 to every civil stormwater estimate and hydraulic estimate we produce — the calculator is built on the same standard.

Spoil volume equals trench width × average depth to invert × length, minus the pipe volume. This calculator does this automatically for each pipe run — enter the DN size, depth to invert and linear metres and total spoil is calculated instantly in both m³ and tonnes.

Trench width is calculated from the pipe OD plus side clearances as per AS/NZS 3500. For government and rail projects SNZ includes complete material schedules with every estimate.

A truck & dog carries 32 tonnes (~23m³ loose). A rigid truck carries 14 tonnes (~10m³). This calculator shows both figures automatically based on your spoil volume — truck & dog for open sites with good access, rigid truck for restricted suburban or tight access sites.

Always confirm load capacities with your haulage contractor. Clean fill spoil is typically taken to fill sites, not tips — haulage cost is per load. SNZ includes excavation and spoil quantities in all high-rise residential and commercial hydraulic estimates.

For excavated clay being removed as spoil, use the loose or bulked density — typically 1.4 t/m³ for clay. Clay expands when excavated (bulking factor of approximately 20-30%) so the loose density is lower than the in-situ compacted density. This is the correct value for truck load estimation and is the default in this calculator.

Do not use compacted density for spoil disposal — it will overestimate your truck load requirements significantly.

For ordering embedment material from a supplier, use the compacted density — 1.8 t/m³ for crushed rock. DGB20 road base as trench fill is typically 2.0 t/m³ compacted. These are the correct values for supplier ordering — compacted density is how the material performs in the trench and how suppliers price it.

SNZ uses these exact density values in industrial, airport and rail project estimates where accurate material ordering is critical.

Yes — unlike dropdown-based calculators with fixed pipe size lists, this calculator accepts any DN size you type. DN100, DN375, DN1500, DN2400, DN3000 — all calculated correctly using the same formula. The trench cross-section diagram updates live to show the correct scale of your pipe relative to the trench.

SNZ has estimated large-diameter civil stormwater for shopping centres, airports and major government infrastructure projects nationally.

The calculator gives accurate theoretical quantities based on the dimensions and parameters you enter. Real quantities vary with soil conditions, pipe manufacturer tolerances, site conditions and contractor methodology — always add a contingency allowance of 10-15% for real project pricing.

For a fully priced, bankable estimate ready for tender submission, SNZ provides complete hydraulic estimates across all sectors and states — individually measured from your drawings, not benchmarked.

No account or subscription required. Three free calculations are available immediately with no login. After three uses a one-time registration is required — name, company and email address only. Once registered the calculator is unlocked permanently on your device at no cost.

Yes. The Share button copies a link that encodes your entire calculation — pipe sizes, depths, linear metres, pits, tanks and material settings. Anyone opening that link gets the calculator pre-filled with exactly what you entered. You can also export a branded PDF report or email the results to yourself directly.

SNZ contractors use this to share preliminary quantities with clients before formal budget pricing or full tender estimates.

SNZ estimates for every major construction sector across Australia — hospitals and healthcare, high-rise residential, commercial and retail, government infrastructure, schools and universities, industrial, fuel stations, shopping centres, airports, McDonald's and rail and train stations.

View our project case studies for real credentials across each sector — 300+ projects across NSW, VIC, QLD, SA, WA, NT and ACT.

Yes — this is exactly what SNZ does. The calculator gives you quantities for budgeting. SNZ gives you a fully priced, bankable hydraulic estimate ready for tender submission — every pipe, fitting and system individually measured and priced from your drawings.

15 years experience, 300+ projects. Available in Sydney, Melbourne, Brisbane, Perth, Adelaide, Canberra and Darwin. Get a quote here or call +61 451 404 645.