Concrete Encasement Calculator
This concrete encasement calculator nets out what estimators often forget: the pipe. It computes the rectangular encasement prism along the run and subtracts the cylinder the pipe displaces — the true concrete volume for pipe and duct encasement.
How to Use This Calculator
- Enter your dimensions — feet for lengths, inches for thickness.
- Adjust the options — waste percentage, bag size and your local concrete price.
- Read your results — volume, bags, weight and cost update live as you type.
The Formula
Net volume = (width × height × length) − π × (pipe Ø ÷ 2)² × length Worked example: An 18 × 18 in encasement over 50 ft around a 6 in pipe: (1.5 × 1.5 × 50) − π × 0.25² × 50 = 112.5 − 9.8 = 102.7 ft³ ≈ 3.8 yd³.
Pipe encasement specs typically call for 6 inches of concrete cover on all sides, which sets the prism: pipe diameter + 12 inches each way. A 6-inch pipe gets an 18 × 18 inch encasement, as in the example.
For multi-conduit duct banks, subtract each conduit: run the calculator once per conduit size and deduct the additional displacements, or conservatively ignore small conduits (a 2-inch conduit displaces only 0.022 ft³ per foot).
Encasement pours flow under and around the pipe — strap or block pipes against flotation before the pour. Empty plastic pipe floats energetically in wet concrete.
Frequently Asked Questions
Common questions about the concrete encasement calculator.
How much concrete to encase a pipe?
Encasement cross-section (width × height) × run length, minus π r² × length for the pipe. The calculator handles both terms.
How much cover does encasement need?
Typically 6 inches of concrete on all sides of the pipe — check the utility's spec; some require 4 inches, telecom banks often 3.
Do I subtract small conduits?
Under 2 inches diameter, the displacement is usually within waste allowance. Above 4 inches, subtract — a 6 in pipe displaces nearly 0.2 ft³ per foot.
Why did my encasement pour float the pipe?
Buoyancy — concrete is 2.4× denser than water. Anchor or weight pipes at 5–10 ft intervals before pouring.
Related Calculators
More tools from the concrete calculator family.