Learn · guide

How to use the pile capacity calculator

A single pile in layered soil: what each input means, how the shaft and base add up, and which number to carry to the pile cap.

All guides Inputs Result Calc sheet Walk-through Mistakes

1. What the calculator does

The pile capacity calculator works out how much load a single pile can carry in the ground. From the soil layers it adds up the shaft friction along the pile and the end bearing at the toe, applies the factors of the design basis, and gives the working and design resistances in compression and tension. It also checks the pile shaft as a concrete section for the ULS loads.

The design basis is SANS 10160-5 Table B.2 or EN 1997-1 R4 (DA2); the shaft is checked to SANS 10100-1. The page badge says it plainly: the α and β coefficients are practice values you can see on the calc sheet.

Pile capacity calculator header with the PASS badge — The header: PASS 71 %, governed by the geotechnical compression capacity.

2. The inputs, group by group

Input	What it means	Typical value
Pile	Type (bored cast in place, CFA, driven precast), round or square, diameter or side, and the length below the cut-off.	bored, ø600, 12 m
Load	Working N per pile and working tension T; leave blank for the capacity only. ULS loads for the shaft check.	N 500 kN
Design	The design basis.	SANS 10160-5 Table B.2
Soil layers	Up to five layers from the ground surface down: soil type, the depth to the bottom of the layer, the strength (c_u for clay, φ′ for sand, q_u for rock), and the unit weights; plus the water table.	clay to 4 m (c_u 50), sand to 20 m (φ′ 34°)

Pile capacity inputs: pile, load and design basis — The pile, the load and the design basis. The capacity for the pile cap (R_all / R_ten) is shown straight away.

Soil layer table with the water table — The soil layers, from the ground down. Each layer runs to the depth given; extend the profile below the pile toe.

3. How to read the result

The sketch draws the pile in the soil with the shaft friction and the base resistance. The capacity card gives the shaft, base and ultimate resistance, the pile weight, the working compression and tension, the ULS design resistances, the group efficiency and the shaft check.

Pile sketch in the soil layers with shaft and base resistance — The pile, toe at 12 m, with the shaft and base resistance drawn. The detail drawings are part of the paid plan.

Capacity card with shaft, base and working resistances — Capacity: shaft / base / ultimate 833 / 1131 / 1964 kN, working 704 / 359 kN; for the pile cap R_all 704 kN. The notes list the practice values used.

The last line is the one to take to the pile cap calculator: R_all / R_ten, the working compression and tension per pile. Read the notes under it: they say which practice values were used (for example the cap on base resistance, and whether the top of the shaft in clay is ignored) and where you can change them.

The badge names the governing check. The checks card counts the passes and the NOT CHECKED items; NOT CHECKED is not a pass, so read which items they are once signed in.

Design checks card for the pile capacity calculator — Design checks: SANS 10160-5 · SANS 10100-1 · 2 pass · 3 not checked.

4. Calc sheet

The result (pass / fail and utilisation) stays free for everyone. Every check with its clause, the calc sheet and the bending schedule are open to signed-in users. Sign in free: 3 designs a month (one calculator, open for 24 hours). Unlimited with a calculator pack.

The full detail drawings are part of the paid plan.

5. A 2-minute walk-through

Open the calculator: a bored ø600 pile, 12 m long, in 4 m of clay over sand, with N 500 kN working.
Read the badge: PASS 71 %; R_all is 704 kN.
Lengthen the pile to 15 m and see the shaft friction grow.
Add a water table at 2 m and see the sand friction drop.
Change the type to driven and compare.

6. Common mistakes

A soil profile that stops at the toe. The base resistance depends on the soil below the toe; extend the profile.
Working loads where ULS loads are asked for, or the other way round. N and T per pile are working loads; the shaft check uses the ULS loads.
One pile’s capacity for a close group. Closely spaced piles carry less each; check the group efficiency.
Practice values as site data. The α and β values are typical; a pile test or the geotechnical engineer’s values come first.
Ignoring the water table. Water lowers the effective stress and the friction in sand.

7. Where it fits

R_all and R_ten go to the pile cap calculator as the pile capacity.

8. Learn more

Try it nowThe calculator opens with the walk-through inputs above. The result is free; sign in for the checks, calc sheet and schedule.
Open the pile capacity calculator

A guide to using the calculator, not a design. Check every value against the current code and your own project, and have the design checked and signed by a registered professional engineer.

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