Pile Quantity Calculator

Work out pile quantity instantly with clear inputs, formula shown and shareable results.

About Pile Quantity Calculator

Pile count is the total load divided by the capacity each pile can actually deliver in a group. Group efficiency is less than one because closely spaced piles share overlapping stress zones, so the group carries less than the sum of isolated piles; 80-90 percent is typical at three diameter spacing.

Formulas

Effective capacity

Q effective = single pile capacity x group efficiency

Pile count

N = ceil(total load / Q effective)

Worked example

With the default values below, Pile Quantity Calculator returns Piles required of 9. Change any input above and every figure here is recalculated in your browser.

Inputs used

Total load to supportminimum 1 kN: 4,500 kN
Safe capacity per pileminimum 1 kN: 600 kN
Pile group efficiencyaccepts 40–100 %: 85 %

Results

Piles required: 9
Effective capacity per pile: 510.0 kN
Total group capacity: 4,590.0 kN
Group utilisation: 98.0% %

Step by step

1Values used
2Effective capacity
3Pile count
4Piles required= 9
5Effective capacity per pile= 510.0 kN
6Total group capacity= 4,590.0 kN
7Group utilisation= 98.0 %

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or compounding frequency into account.
Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Preliminary estimate only. Pile group design must be carried out by a qualified geotechnical engineer including settlement, eccentricity and lateral load checks.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Pile group design must be carried out by a qualified geotechnical engineer including settlement, eccentricity and lateral load checks.

Frequently Asked Questions

How is the Pile Quantity figure worked out?

Q effective = single pile capacity x group efficiency. Pile count is the total load divided by the capacity each pile can actually deliver in a group.

Does wider spacing remove the penalty?

Largely. At spacings beyond about six diameters interaction becomes small, but the pile cap grows and its cost usually outweighs the saving in pile numbers.

What values do I need to enter?

This calculator takes 3 inputs: Total load to support, Safe capacity per pile, Pile group efficiency. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.