Work out pile quantity instantly with clear inputs, formula shown and shareable results.
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.
Effective capacity
Q effective = single pile capacity x group efficiency
Pile count
N = ceil(total load / Q effective)
Preliminary estimate only. Pile group design must be carried out by a qualified geotechnical engineer including settlement, eccentricity and lateral load checks.
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.
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.
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.