Rectangular Tank Volume Calculator
By Santaji GadepatilinUpdated October 27, 2026
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Type in any field to change it. Press × on a value to calculate that field instead.
How to use this calculator
Enter the tank’s inside length, width and water depth. The capacity and the weight of the water are calculated. Find the water depth for a given volume by typing the volume instead.
Example
A 2 × 1.5 m tank filled to 1.2 m:
V = 2 × 1.5 × 1.2 = 3.6 m³ = 3,600 litres (951 US gal), weighing about 3.6 tonnes.
For round tanks use the cylinder calculator, and for horizontal cylindrical tanks the horizontal tank calculator.
Frequently asked questions
How do I calculate tank capacity in litres?
Multiply length × width × height in metres to get m³, then multiply by 1,000.
How much does the water weigh?
About 1 kg per litre — a 3,600-litre tank holds about 3.6 tonnes, so the base or roof slab must be designed for it.
How do I size a tank for a household?
Estimate daily use (often 100–150 litres per person) and multiply by the days of storage you want.