Tank & Trench Calculators
Explore our suite of free tank & trench calculators to precisely estimate volume, weight, and costs for your next project. Select a tool below to get started.
Tank or Trench Concrete Calc
Calculate concrete volume for tanks or trench structures easily.
Flowable Fill (CLSM) Calculator
Calculate CLSM volume in yd³, ft³, and m³ for utility trenches, abandoned tanks/vaults, and pipe or culvert fill — with overfill factor, weight at 100–125 pcf, and ACI 229R compliance check.
Estimating Concrete for Tanks and Trenches
Water tanks, septic tanks, and utility trenches require estimating hollow concrete structures. This involves calculating outer dimensions to establish a total outer volume, and subtracting the inner hollow void dimensions. You also must separately calculate the floor and roof slabs of a closed tank.
Core Formula
Wall Volume = (Outer L × Outer W) - (Inner L × Inner W) × Height
Frequently Asked Questions
- How do I calculate the concrete needed for trench walls?
- Measure the total linear run of the trench. Then calculate the volume of the two parallel wall segments along the sides.
- Do I calculate the floor of a tank separately from the walls?
- Yes. Calculate the floor slab as a standard rectangular pour covering the entire outer footprint. Then calculate the hollow wall structure extending upward from the slab.
- What is a retaining trench?
- A retaining trench (or keyway) is a trench dug beneath a retaining wall to lock the base of the wall securely against lateral soil movement.
- Should I account for pipe openings in a tank wall?
- Unless the pipes are exceptionally large (over 12 inches in diameter), it is standard practice to ignore small penetrations during estimating. The 'extra' concrete simply becomes a safety margin.