Road Set-out Offset Table Builder
A free, browser-based tool. Runs entirely in your browser — no sign up, nothing stored.
Road set-out points
| Chainage | Centreline RL | Offset (m, − left) | Crossfall (%) | |
|---|---|---|---|---|
Crossfall is signed — a typical sealed road falls away from the crown at about −2.5%. Runs in your browser.
Offset RLs
| Chainage | CL RL | Offset | Fall | Offset RL |
|---|---|---|---|---|
| 0.000 | 50.000 | 3.000 | -0.075 | 49.925 |
| 0.000 | 50.000 | -3.000 | +0.075 | 50.075 |
| 20.000 | 49.600 | 3.000 | -0.075 | 49.525 |
How to use this calculator
- For each set-out point, enter the chainage, the centreline RL, the offset (− for left of centre) and the crossfall.
- Add a row per offset you need (e.g. left and right edges at each chainage).
- Read the offset RL and the fall from the centreline.
How it works
The offset RL is the centreline RL plus the offset times the crossfall: offset RL = CL RL + offset × (crossfall ÷ 100).
Crossfall is signed — a sealed road normally falls away from the crown at about −2.5%, so a +3 m offset at −2.5% drops 75 mm below the centreline.
Worked example
Edge 3 m right at −2.5%. Centreline RL 50.000, offset +3 m, crossfall −2.5% → fall −0.075 m, so the edge RL is 49.925.
Frequently asked questions
How do I set out both edges?
Add two rows at the same chainage — one with a positive offset (right) and one negative (left). Both use the same crossfall unless your design says otherwise.
Is this official course material?
No. It is free study support mapped to surveying course levels — not official North Metropolitan TAFE content or advice. Always follow your lecturer and the official assessment brief, and check your own working.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.