About

A pile cap is a critical structural element that distributes column loads to a group of piles. The structural integrity depends heavily on the volume of concrete and the density of steel reinforcement. This tool computes the necessary materials for a rectangular pile cap, providing a detailed Bill of Quantities for cost estimation.

Accurate material estimation prevents onsite shortages (which cause cold joints) and reduces wastage. This calculator considers the "cover" (distance from concrete surface to rebar) to determine the effective cutting length of the steel bars. It assumes a standard two-way reinforcement mesh at the bottom of the cap.

Formulas

The total concrete volume is a straightforward geometric calculation:

V_conc = L × W × D

Total Rebar Weight is calculated by determining the number of bars in both X and Y directions, multiplying by their cut lengths and specific unit weights:

W_steel = (N_x × L_x + N_y × L_y) × w_unit

Where N_x (Number of bars along X) is:

N_x = L - 2cspacing + 1

Reference Data

Rebar Size (US)	Rebar Size (Metric)	Weight (kg/m)	Weight (lb/ft)
#3	10 mm	0.617	0.376
#4	13 mm	0.994	0.668
#5	16 mm	1.552	1.043
#6	19 mm	2.235	1.502
#7	22 mm	2.980	2.044
#8	25 mm	3.853	2.670

Frequently Asked Questions

Concrete cover is the distance between the outer surface of the concrete and the nearest reinforcing bar. For foundations in contact with the ground, this is typically 50mm to 75mm (2-3 inches) to protect the steel from corrosion.

No. This tool calculates the materials for the "cap" (the block on top). Pile depth is determined by geotechnical soil reports and load capacity requirements.

Steel reinforcement is sold by weight (tonnes or kg). Accurate weight calculation is essential for ordering the correct quantity and estimating transport costs.

Pile caps typically require high-strength concrete, often M25, M30, or higher (3000-4000 PSI), depending on the structural design.