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.
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.