Differential Settlement Calculator Form
Use this form to compare two support points, estimate distortion, and review a quick serviceability check.
Formula Used
1) Differential settlement
Δ = |SA - SB|
2) Angular distortion or settlement slope
β = Δ / L
3) Equivalent ratio form
1 : n, where n = L / Δ
Where:
- SA = settlement at support A
- SB = settlement at support B
- Δ = differential settlement
- L = horizontal distance between supports
- β = dimensionless angular distortion
These formulas help compare support movement, estimate tilt severity, and perform a quick serviceability screening for slabs, beams, walls, and foundation lines.
How to Use This Calculator
- Enter the settlement measured at Point A.
- Enter the settlement measured at Point B.
- Select the settlement unit you want to use.
- Enter the spacing between the two supports.
- Select the distance unit for that spacing.
- Add the reference elevation if you want a simple profile estimate.
- Enter an allowable distortion ratio, such as 1:500.
- Click Calculate Settlement to view the results above the form.
- Use the CSV or PDF button to save the calculation summary.
Example Data Table
| Case | Settlement A (mm) | Settlement B (mm) | Distance (m) | Differential Settlement (mm) | Approx. Ratio |
|---|---|---|---|---|---|
| Footing Line 1 | 10 | 18 | 4.0 | 8 | 1:500 |
| Footing Line 2 | 12 | 28 | 6.0 | 16 | 1:375 |
| Wall Segment A | 6 | 9 | 3.0 | 3 | 1:1000 |
| Slab Strip C | 4 | 14 | 5.0 | 10 | 1:500 |
Frequently Asked Questions
1) What is differential settlement?
Differential settlement is the difference in vertical movement between two points of a structure or foundation. It matters because uneven movement can crack walls, distort frames, and reduce serviceability even when total settlement seems modest.
2) Why is angular distortion important?
Angular distortion shows how rapidly settlement changes over a given length. Engineers use it to judge tilt severity, cracking risk, and serviceability problems in structural and nonstructural elements.
3) Which units can I use here?
You can enter settlement in millimeters, centimeters, meters, inches, or feet. Distances can also be entered in several common units, and the calculator converts them internally for consistent calculations.
4) What does the ratio 1:n mean?
The ratio 1:n expresses the slope form of settlement distortion. A larger n means a gentler change in level. For example, 1:1000 is flatter than 1:300.
5) Is this calculator enough for final design?
No. This tool is excellent for screening and quick checks, but final foundation design should also consider soil profile, stiffness, load path, groundwater, time effects, and structural tolerance limits.
6) What causes differential settlement?
Common causes include variable soil stiffness, uneven loading, poor compaction, moisture changes, erosion, nearby excavation, organic material decay, or inconsistent foundation geometry.
7) Can total settlement be acceptable while differential settlement is not?
Yes. A structure may tolerate moderate uniform settlement, yet perform badly under uneven movement. Differential settlement often drives cracking, binding doors, façade damage, and drainage issues.
8) How should I choose the allowable ratio?
Use project criteria, code guidance, structural type, and finish sensitivity. Buildings with brittle finishes or strict equipment alignment usually require tighter allowable limits than flexible structures.