Free Australian DIY earthworks tool
Planning a backyard dig, retaining wall, trench, post-hole job or site cut? Enter your excavation dimensions, access and ground conditions to estimate in-ground volume, loose spoil, a suitable mini excavator class and indicative active digging time.
This is a planning guide, not engineering or safety certification. Site conditions, underground services, slopes, lifting and access can change what is suitable.
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Calculate excavation volume, loose spoil and mini excavator size
This free Australian planning tool combines job geometry, access, ground conditions and operator inputs so you can think about the whole excavation rather than only cubic metres. If you want the selection principles before running a calculation, read our guide to choosing the right mini excavator size. For tight sites, our mini excavator access measuring guide explains what to check around gates, turns and overhead restrictions.
How this mini excavator calculator works
The calculator uses your stated access width, excavation dimensions, ground type, spoil-handling plan, project type and operator experience. It calculates in-ground volume, applies a material-dependent loose-spoil allowance, checks the entered dimensions against Digger2Hire machine limits and, where the job can be modelled responsibly, gives a broad range for active machine time. It does not assume that the biggest machine is automatically the best choice.
Compare 0.9T, 1.7T, 2.5T and 5.5T excavators
Use this quick comparison as a planning reference. The calculator applies the entered access and job details before recommending a machine; published dimensions alone do not guarantee that a machine can safely reach or complete a particular job.
| Machine | Minimum / stated width | Standard height | Maximum dig depth |
|---|---|---|---|
| Kubota K008-3 0.9T | 700 mm retracted | 2,230 mm upright ROPS | about 1,720 mm |
| Kubota U17-3 1.7T | 990 mm | 2,340 mm canopy | 2,310 mm |
| Kubota U25-3 2.5T | 1,500 mm | 2,420 mm canopy | 2,810 mm |
| Yanmar ViO55-6B 5.5T | 1,990 mm | about 2,540 mm canopy | up to 3,900 mm with quick coupler |
Digger2Hire access notes
- K008-3: its foldable ROPS reduces height to approximately 1,790 mm for passing a low obstruction. The ROPS should be raised and locked again for normal operation.
- U17-3: Digger2Hire treats temporary canopy removal as a low-clearance access option only from 2,000 mm stated clearance, with the canopy refitted before normal operation.
- U25-3: no special low-clearance exception is assumed by this calculator; the complete access route must suit the stated machine dimensions.
- ViO55-6B: included here for size comparison only. The current calculator does not produce a calibrated active-time estimate for the 5.5T.
Specification sources: Kubota manufacturer data for K008-3, U17-3 and U25-3S; Yanmar manufacturer data for ViO55-6B. The access notes above are Digger2Hire operational assumptions, not manufacturer dimensions. Sources reviewed 7 September 2026.
Methodology & assumptions
How access width and overhead clearance affect machine choice
A machine can be powerful enough for the job but still be unsuitable if it cannot reach the work area. The calculator treats access as a practical constraint before productivity. Measure the narrowest clear opening, including gate hardware and fixed obstructions, and consider turns, slopes, uneven ground and the space needed to manoeuvre. A dimension that only just clears a published machine width is not the same as a guaranteed access route.
How loose spoil volume and weight are estimated
In-ground volume is calculated from the entered geometry. For rectangular excavation this is length × width × average excavation depth; post-hole volume is added when post holes are part of the selected job. Excavated material usually occupies more space after it is disturbed, so the calculator applies the planning factors below.
| Ground type | Loose-spoil factor | Planning density of loose spoil |
|---|---|---|
| Topsoil | 1.20× | 1.35 t/m³ |
| Sand | 1.12× | 1.60 t/m³ |
| Clay | 1.28× | 1.75 t/m³ |
| Gravel / rocky fill | 1.18× | 1.80 t/m³ |
| Unknown / mixed | 1.22× | 1.60 t/m³ |
These are Digger2Hire planning assumptions used by the calculator, not laboratory measurements of your material. Moisture, compaction, rock content and mixed fill can materially change actual loose volume and weight.
How indicative active digging time is estimated
Machine time is deliberately shown as a range, not a promise. The estimate considers the excavator size, excavation volume, ground conditions, operator experience, slope, manoeuvring space, spoil handling, project type, excavation depth and awkward-material handling. These factors can significantly change how quickly excavation progresses, even where two projects involve the same volume of material.
The estimate is active machine time. It excludes delivery, handover, set-out, breaks, hand digging, service locating, dewatering, shoring, unexpected rock or roots, truck waiting and off-site spoil transport. Significant slopes and rock/root-removal jobs are intentionally not given a volume-only time estimate because site conditions dominate the result.
Calculator assumptions and limitations
- All measurements are treated as user-supplied planning measurements; Digger2Hire has not inspected the site.
- Maximum manufacturer digging depth does not guarantee that a machine is suitable for a particular excavation, batter, trench or structure.
- Access checks use stated dimensions and Digger2Hire operational rules; they do not account for every turn, camber, slope, soft edge or obstacle.
- Underground and overhead services, ground stability, lifting, shoring and other hazards require separate assessment.
- Results are an initial planning guide, not engineering advice, a site assessment or a booking confirmation.
Mini excavator calculator FAQs
Why is loose spoil greater than the hole or trench volume?
Digging breaks up the compacted material and creates voids between particles and lumps. The calculator therefore applies a ground-type bulking allowance before estimating loose volume and weight.
How should I measure excavator access?
Measure the narrowest clear width and lowest clear height along the complete route, not just the gate opening. Include hinges, posts, pipes, eaves, branches, turns and uneven ground. See our access measuring guide.
Does maximum digging depth mean the excavator can safely dig my project?
No. Maximum digging depth is a machine specification, not a site-suitability guarantee. Reach, working position, ground stability, services, shoring, spoil placement and access can all change what is practical or safe.
Why is machine time shown as a range?
Operator experience, ground resistance, machine positioning and where the spoil must go can change production dramatically. A range is more honest than presenting a precise completion time that the calculator cannot guarantee.
What if the calculator says no Digger2Hire machine is suitable?
Re-check the measurements first. If they are correct, the job may need a different access plan, a different machine class or site-specific advice rather than forcing a machine recommendation.
Unsure whether the machine can physically reach the work area? Run the Mini Excavator Access Checker.