How to Calculate Water Tank Capacity in Litres

🚰 Planning to install a water tank or check how much water you have? Here’s how to calculate the volume — in litres!

Whether you’re setting up a rainwater tank, checking how much water your storage can hold, or just curious, it’s easy to calculate your tank’s capacity in litres — once you know the shape.

Let’s break it down by tank shape and give you step-by-step examples.

🧮 What You’ll Need

To calculate water tank capacity in litres, you need:

• The tank’s dimensions (length, width, height or radius, depending on shape)
• The shape of the tank (cylindrical, rectangular, or cube)
• A basic formula for volume
• And then a quick conversion to litres

📐 Formula to Convert Volume to Litres

1 cubic meter = 1,000 litres
1 cubic centimetre = 0.001 litres

So once you calculate the volume in cubic meters (m³), just multiply it by 1,000 to get litres.

📦 Rectangular or Square Tank

Formula:

Volume = Length × Width × Height

Make sure all dimensions are in meters for litres.

Example:

Tank dimensions:

• Length = 1.5 m
• Width = 1 m
• Height = 1.2 m

Volume = 1.5 × 1 × 1.2 = 1.8 m³  
Capacity = 1.8 × 1000 = 1,800 litres

✅ This tank holds 1,800 litres

🛢️ Cylindrical Tank

Formula:

Volume = π × r² × h

Where:

• r = radius (in meters)
• h = height (in meters)

Example:

Tank dimensions:

• Radius = 0.5 m
• Height = 2 m

Volume = 3.1416 × (0.5)² × 2 ≈ 1.57 m³  
Capacity = 1.57 × 1000 = 1,570 litres

✅ This tank holds about 1,570 litres

🧊 For Cube-Shaped Tank

Just cube the side:

Volume = side × side × side

Then convert to litres.

✅ Quick Tips

• Always convert cm to meters: 100 cm = 1 m
• For cylindrical tanks, don’t confuse diameter with radius (radius = diameter ÷ 2)
• Multiply volume in m³ by 1,000 to get litres