How to use the Water Cubic Feet Calculator
- Choose a rectangle or full cylinder and measure the inside dimensions. Diameter is across the centre of the cylinder.
- Choose rectangular or cylindrical capacity. Enter inside dimensions and the water density used for the optional weight estimate.
- Select Calculate. Review the result and its working; if you change an input, calculate again before copying or sharing.
Water formula
The chosen container model gives full internal volume. US liquid gallons and water weight are calculated from that volume.
Rectangle: length × width × depth; cylinder: π × (diameter ÷ 2)² × height
What the terms mean
- Interior length
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Interior width
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Interior height / depth
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Interior diameter
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Number of identical items
- The whole-number count of objects with the same entered dimensions.
- Water density
- The mass of water per cubic foot under the conditions being estimated.
Water worked examples
Estimate a rectangular container capacity
A full rectangular container has inside dimensions of 4 ft × 3 ft × 2 ft. The example water density is 62.4 lb/ft³.
- length × width × depth × quantity
Answer: 24 ft³. Cubic yards: 0.888889 yd³; Litres: 679.604318 L; US gallons: 179.532468 US gal; Estimated water weight: 1,497.6 lb.
Estimate a full cylindrical water container
A cylinder has an inside diameter of 2 ft and height of 4 ft. Use a water density of 62.4 lb/ft³ for the illustrative weight.
- π × (diameter ÷ 2)² × height × quantity
Answer: 12.566371 ft³. Cubic yards: 0.465421 yd³; Litres: 355.839989 L; US gallons: 94.00298 US gal; Estimated water weight: 784.141526 lb.
Water Cubic Feet Calculator FAQs
Is a US gallon the same as an Imperial gallon?
No. This page explicitly uses the US liquid gallon, equal to 231 cubic inches.
Can I calculate a partly filled tank?
Use the tank page for a liquid-depth calculation, including horizontal cylinders.
Measurement guide for Water
Use inside dimensions for capacity. This tool models a full container; for a partly filled vessel, use the tank calculator.
Assumptions and limits
Capacity excludes wall thickness. The default density is approximate fresh water; dissolved salts and temperature can change it.
Full interior capacity. Water density is approximate and depends on temperature.
Check your result
Check full capacity against the inside dimensions. The gallon result uses US liquid gallons, and weight depends on the stated water density.