| Scenario | Piers | Diameter (m) | Depth (m) | Rates (drill / conc / rebar) | Notes |
|---|---|---|---|---|---|
| Small building | 12 | 0.60 | 10.0 | $140/m³, $120/m³, $1.20/kg | Totals vary by spoil, casing, and markups |
| Medium bridge bent | 20 | 1.00 | 18.0 | $180/m³, $135/m³, $1.35/kg | Depth drives production limits and testing |
| Industrial heavy load | 30 | 1.20 | 22.0 | $210/m³, $150/m³, $1.40/kg | Casing and contingency are often higher |
- Enter pier count, shaft diameter, and depth.
- Enable the bell option if your design requires it.
- Set overbreak, waste, and slurry allowances.
- Select rebar method and add ratio or cage details.
- Enter drilling, concrete, rebar, spoil, and casing rates.
- Apply contingency, overhead, and tax values if needed.
- Press Estimate Cost to view results above.
Cost drivers you can quantify early
Drilled pier cost is mostly controlled by excavation volume, concrete volume, and reinforcement weight. This estimator converts diameter and depth into cubic meters, then prices drilling, concrete, and steel. Use the access factor to reflect production limits, overhead clearance, staging, or night shifts.
Typical allowance ranges that affect totals
Overbreak is commonly 3–10% in firm soils and higher where caving or cleanup is frequent. Concrete waste often runs 2–6% depending on tremie placement, truck waiting, and cutoff trimming. If slurry is used, handling and disposal can increase spoil volume by 5–15%. When rock sockets are required, consider a higher drilling rate rather than inflating overbreak.
Rebar estimating options for different design maturity
When drawings are not final, a rebar ratio of 90–140 kg/m³ is a practical starting band for many building piers; heavily loaded elements may exceed this range. For detailed cages, the calculator uses bar count, bar diameter, tie spacing, cover, and a lap factor to approximate total kilograms. Tie length is based on an internal circumference estimate, so confirm cover and cage diameter. Replace these inputs with bar schedules when available.
Temporary casing and disposal planning
Casing requirements vary by groundwater, loose strata, vibration limits, and nearby structures. Enter casing length per pier and a reuse credit if casing is rotated across multiple shafts. Spoil disposal is priced per cubic meter; confirm whether disposal includes hauling, drying, dewatering, or slurry treatment, because those items can dominate on constrained sites. If disposal is priced per truckload, convert to an equivalent cost per cubic meter for consistent comparisons.
Markup structure for bid-ready summaries
The build-up follows a common estimating sequence: direct costs plus mobilization, then contingency, overhead and profit, and finally tax. This keeps each layer transparent for approvals. For competitive bids, tune contingency by geotechnical uncertainty, drilling method, and schedule risk. Record productivity assumptions, such as piers per day and concrete placement windows, and attach the exported report to your internal estimate log.
What does the estimate include by default?
It prices drilling, concrete, reinforcement, spoil disposal, testing per pier, and mobilization. Then it applies access adjustment, contingency, overhead and profit, and optional tax. Update unit rates to match your supplier quotes and subcontractor bids.
Why are results shown in cubic meters and kilograms?
The calculator converts imperial or metric inputs into metric quantities to keep formulas consistent. You can still enter feet or inches in the form. Use the currency symbol field to match your market and reporting format.
How should I choose an overbreak percentage?
Start with 5% for steady shafts in competent soils. Increase the value where cleanup, sloughing, or irregular sides are expected. If rock is present, adjust the drilling rate first, then fine‑tune overbreak.
When should I use the detailed rebar method?
Use it when you know bar counts, diameters, tie spacing, and cage extension requirements. It is better for pricing steel and fabrication. If design is early, the ratio method is faster and usually adequate for budgeting.
How do I handle casing that is reused?
Enter the casing length per pier, then set a reuse credit percentage. A 50% credit assumes half of the casing cost is avoided through reuse across multiple shafts. If casing is rented, use a rate that already reflects rental terms.
Can I use this for rock sockets or micropiles?
You can approximate rock sockets by increasing the drilling rate for the socketed portion and adjusting depth. Micropiles have different materials, drilling methods, and grouting assumptions, so treat results as a rough order‑of‑magnitude only.