Calculator
Enter details below. Results appear above this form.
Example Data Table
Common scenarios and typical recommendations. Always confirm with your anchor or fixture specs.
| Scenario | Tile type | Input | Typical drill bit approach |
|---|---|---|---|
| Shower shelf bracket | Porcelain | M6 screw + plastic plug | Diamond bit, ~7–8 mm hole, low RPM |
| Towel hook | Ceramic | #8 screw + plug | Carbide spear-point, ~5–6 mm hole |
| Toilet supply line pass-through | Marble | 20 mm pipe OD | Diamond core, ~26–28 mm hole, wet |
| Glass backsplash fixture | Glass | Custom 6 mm hole | Diamond spear-point, ~7–8 mm with clearance |
Formula Used
This calculator uses simple, practical sizing rules to reduce cracking and binding.
- Screw / anchor hole: Bit(mm) = Screw(mm) + Clearance(mm) + AnchorAllowance(mm)
- Pipe / fixture hole: Bit(mm) = PipeOD(mm) + 2×SideClearance(mm) + Clearance(mm)
- Custom hole: Bit(mm) = DesiredHole(mm) + Clearance(mm)
Clearance is chosen by tile hardness, then adjusted slightly for thicker tiles.
This aims for a clean hole that fits without forcing.
How to Use This Calculator
- Select a use case for your hole.
- Choose your tile type and enter thickness.
- Enter the size inputs for screws, anchors, pipes, or custom holes.
- Pick a rounding option, then press Calculate.
- Use the recommended bit size, then drill slowly with light pressure.
For large holes, choose a diamond core bit close to the final size.
Start at a slight angle, then level the drill once it bites.
Safety and Accuracy Notes
- Use painter’s tape to stop bit skating on glossy tile.
- Do not use hammer mode on tile; switch after passing tile.
- Keep the bit cool to prevent micro-cracks and blowouts.
- When anchors matter, follow the anchor brand sizing chart.