Water Tank Volume Calculator

Choose tank geometry.

Longest dimension (rectangular) or diameter (cylinder/sphere).

Required for rectangular tanks.

Water depth or tank height.

Partial fill for horizontal cylinder.

To estimate fill/drain time.

Mastering Water Tank Volume: A Comprehensive Guide

The Water Tank Volume Calculator determines storage capacity for common tank shapes using exact geometric formulas. It supports full or partial fill, unit conversion (gallons, liters, ft³, m³), and time estimation. This guide explains volume equations, practical applications, sizing rules, and plumbing considerations for reliable water systems.

What is Tank Volume?

Volume = space enclosed by tank walls. Common units:

  • Gallon (US): 1 ft³ = 7.4805 gal
  • Liter: 1 ft³ = 28.3168 L
  • Cubic Meter: 1 m³ = 264.172 gal

Why Calculate Tank Volume?

Accurate volume ensures:

  • Proper Sizing: Meets demand (fire, domestic, irrigation).
  • Pump Selection: Flow rate and head.
  • Chemical Dosing: Treatment concentration.
  • Cost Control: Avoid oversizing.

Use with our Rainwater Harvesting Calculator for collection.

Volume Formulas

ShapeFormulaNotes
RectangularV = L × W × HFull height
Vertical CylinderV = π r² hr = D/2
Horizontal CylinderV = L × π r² × (θ - sin θ)/360Partial fill
SphereV = (4/3) π r³r = D/2

How to Use the Calculator

Step-by-step:

  1. Select Shape: Match your tank.
  2. Enter Dimensions: In feet or meters.
  3. Set Fill Level: 100% for full, less for partial.
  4. Add Flow Rate: For time estimate.
  5. Get Results: Instant volume and time.

Practical Applications

Used for:

  • Fire Suppression: NFPA 22 storage.
  • Domestic Supply: 2-day reserve.
  • Irrigation: Crop water requirement.
  • Aquaculture: Fish stocking density.

Pair with our Concrete Volume Calculator for tank construction.

Tips for Accurate Measurement

Best practices:

  • Measure Inside: Exclude wall thickness.
  • Use Level: For horizontal cylinders.
  • Account for Fittings: Subtract 5–10%.
  • Check Units: Consistent (ft or m).

Common Mistakes to Avoid

Avoid:

  • Using Outside Dimensions: Overestimates volume.
  • Ignoring Partial Fill: For horizontal tanks.
  • Wrong Units: gal vs liter confusion.
  • No Safety Factor: Undersized reserve.

Advanced Considerations

For special cases:

  • Elliptical tanks: Use average diameter.
  • Thermal expansion: Add 10% headspace.
  • Pressure vessels: ASME design.
  • Multiple tanks: Sum volumes.

Conclusion

Water tank volume is critical for system design and operation. Our Water Tank Volume Calculator delivers instant, accurate results for any shape. Combine with our Steel Weight Calculator for supports. Explore our full suite of Construction Calculators for complete water management.