Bedding & Spoil Calculator
Per-run accuracy. Per-run materials. Per-run bedding.
The most accurate free trench calculator in Australia — calculates bedding, embedment, trench fill and spoil removal quantities for every pipe run independently. Per-run depth, per-run soil type, per-run bedding overrides, automatic AS/NZS 3500 compliance, formula entry in cells, mixed-material tonnes conversion, truck load estimates and live trench diagram. Engineering accuracy a generic calculator cannot provide.
Each pipe run has its own soil type, embedment material and trench fill material. Mixed-material jobs calculate correct weighted tonnes — run 1 in clay, run 2 in sand, totalled accurately. No other free tool does this.
Type 23+14.5+8 directly into any linear-metre field. Sum, subtract, multiply, divide. No more sitting with a separate calculator totalling runs before entry.
Bedding below, bedding above and side clearance override globally or per run. DN100 at 75mm bed and DN1500 at 150mm bed — both correct in the same job. Advanced Bedding Options on every row.
Minimum cover checked automatically — 300mm unpaved, 500mm paved. Depth adjusts instantly if required, with a clean inline notification. No manual checking needed.
Three separate density categories — loose/bulked for spoil disposal, compacted for embedment ordering, compacted for trench fill. Each with multiple material options. The way engineers actually think.
Cross-section diagram scales live with your pipe size — pipe outer wall, embedment, trench fill, side clearance arrows all reposition dynamically. See exactly what you are estimating.
Spoil removal loads for truck & dog (32t, ~23m³) and rigid truck (14t, ~10m³). Open and restricted access sites calculated separately. Disposal logistics built in.
Branded PDF, email to yourself or copy a shareable link that pre-fills the entire calculation for colleagues. Job reference field on every export.
No credit card, no subscription, no software. Three free calculations then a one-time registration. Used daily by Australian plumbing contractors.
How it works
23+14.5+8 directly into the cells. Add as many pipe sizes as the job needs.Mixed-material jobs calculate correctly — not averaged.
Real jobs have multiple pipe sizes through multiple soil types. Run 1 may sit in sandy loam at 1.5 t/m³. Run 2 may be in clay at 1.4 t/m³. Generic calculators apply one density to the whole job and produce a wrong total. SNZ’s calculator handles each run independently, converts each volume to tonnes using its own material density, and totals the weighted figures correctly.
Same logic for embedment and trench fill — coarse sand, crushed rock, DGB20, road base. Each run carries its own material. The tonnes figure you see is the tonnes you actually need to order. This is what separates an estimating tool from a marketing widget.
AS/NZS 3500 minimum cover — 300mm unpaved, 500mm paved — applied automatically. Bedding below defaults to 75mm, above to 100mm, side clearance to 100mm. Spoil density defaults to clay (1.4 t/m³ loose). Embedment defaults to crushed rock (1.8 t/m³ compacted). Trench fill defaults to DGB20 road base (2.0 t/m³ compacted). All values overridable globally or per pipe run.
Bedding & spoil
calculator.
Calculate excavation volumes for pipes, pits and below-ground structures. Built on AS/NZS 3500 standards.
Enter your business details to continue. Takes 30 seconds — unlocks permanently on this device.
Business emails only. We respect your privacy.
Pit depths use avg depth to IL. Defaults to 1.0m if not entered.
Line-by-line results appear here as you enter values above.
SNZ gives you the complete estimate.
Every pipe, pit, GPT, OSD system and civil reinstatement item individually measured from your actual drawings. Submission-ready. Defensible. Within 1 week for standard civil stormwater scopes.
Questions about the
bedding & spoil calculator.
Real questions from contractors using the calculator — answered honestly. Need a full hydraulic estimate? Call +61 451 404 645 or send your plans and we will respond within a few hours.
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.
Need a complete
hydraulic estimate?
The calculator gives you quantities. SNZ gives you a fully priced, bankable estimate ready for tender — delivered fast.