Calculator Inputs
Use the same vertical datum for collar and bottom elevation. Enter depth-based values in the selected unit system.
Example Data Table
| Case | Collar Elev. (m) | Bottom Elev. (m) | Diameter (mm) | Inclination (°) | Design Depth (m) | Volume (m³) | Casing Coverage (%) |
|---|---|---|---|---|---|---|---|
| Municipal Well | 125.00 | 79.00 | 150.00 | 4.00 | 49.80 | 0.88 | 80.32 |
| Geotechnical Bore | 210.00 | 128.00 | 200.00 | 6.00 | 90.70 | 2.85 | 77.18 |
| Foundation Probe | 84.00 | 56.00 | 100.00 | 2.00 | 29.42 | 0.23 | 74.78 |
Formula Used
TVD = Collar Elevation − Bottom Elevation
MD = TVD ÷ cos(θ)
Design Depth = MD × (1 + Allowance ÷ 100)
Water Column = Design Depth − Static Water Level
Volume = π × (Diameter ÷ 2)2 × Design Depth
Coverage % = (Casing Length ÷ Design Depth) × 100
θ is inclination from vertical. Use consistent elevation references for reliable depth estimates.
How to Use This Calculator
- Select metric or imperial units.
- Enter collar elevation and bottom elevation using the same datum.
- Provide static water level below ground surface.
- Enter casing length and bore diameter.
- Input inclination from vertical for angled bores.
- Add the desired overdrill allowance percentage.
- Press the calculate button to view results above the form.
- Review the graph, then export results as CSV or PDF.
Frequently Asked Questions
1. What does this bore depth calculator estimate?
It estimates true vertical depth, measured bore depth, design depth, water column height, casing coverage, uncovered depth, and bore volume from common drilling inputs.
2. Why are both collar and bottom elevation needed?
They define the elevation difference across the bore. That difference becomes the true vertical depth when both points use the same reference datum.
3. What is the difference between vertical and measured depth?
Vertical depth is straight down. Measured depth follows the actual bore path. They match only when the bore is perfectly vertical.
4. Why is inclination included?
Inclination adjusts the bore path length. Even a small angle increases measured depth compared with the pure vertical depth.
5. What does overdrill allowance do?
It adds extra depth beyond the calculated path length. Engineers often include this margin for construction tolerance, cleanup, or final design intent.
6. What does water column height represent?
It shows the length of water standing inside the design bore below the static water level. This helps with storage and pump planning.
7. Can I use this page with feet and inches?
Yes. Choose imperial units. Elevation, casing, and water level use feet. Bore diameter uses inches in that mode.
8. Are these results suitable for final field decisions?
They are useful for planning and quick checks. Final drilling decisions should still be verified against survey data, site logs, and design standards.