litre calculator

What is a litre?

A litre (L) is a metric unit of volume. It is equal to one cubic decimetre, which means a cube that is 10 cm × 10 cm × 10 cm has a volume of exactly 1 litre. Litres are widely used for liquids like water, fuel, milk, and chemicals, but they are also useful for container sizing, aquariums, tanks, and industrial measurements.

If you work across different systems, litre conversions become important fast. For example, some countries use gallons for fuel, many product labels use millilitres, and engineers may work in cubic metres. A reliable litre calculator helps you move between these units quickly and with fewer mistakes.

How this litre calculator works

1) Convert units to litres

Choose Convert units to litres when you already have a volume value in one unit and want the equivalent in litres. This is ideal for day-to-day conversion tasks such as:

• Converting mL to L for recipe prep
• Converting cubic feet to litres for storage calculations
• Converting US or UK gallons to litres for fuel or water planning

2) Rectangular tank volume

Use this mode for box-shaped containers: water tanks, fish tanks, troughs, and utility bins. Enter length, width, and height in your chosen unit. The tool calculates total litres and, if needed, litres at a specific fill percentage.

3) Cylindrical tank volume

Use this mode for drums, silos, and round tanks. Enter diameter and height, then select unit type. The calculator applies the cylinder volume formula and returns litres, including partial fill if you set a fill percentage.

Common litre conversion references

• 1 litre = 1000 millilitres
• 1 cubic metre = 1000 litres
• 1 US gallon = 3.785411784 litres
• 1 UK gallon = 4.54609 litres
• 1 cubic foot = 28.316846592 litres
• 1 cubic inch = 0.016387064 litres

Practical examples

Aquarium sizing

Suppose your aquarium is 120 cm long, 40 cm wide, and 50 cm high. In rectangular mode, this gives a total capacity of 240 litres. If you plan to fill to 90%, usable water is about 216 litres.

Rainwater collection

A cylindrical barrel with a 60 cm diameter and 100 cm height holds around 282.7 litres when full. If you keep it at 80% for overflow safety, your practical capacity is about 226.2 litres.

Fuel planning

If your trip estimate is in US gallons but your local station shows litres, convert before you budget. This is especially useful for rentals, road trips, and cross-border travel where measurement systems differ.

Tips for accurate volume calculations

• Always double-check the input unit (cm vs mm is a common source of error).
• For tanks, measure inside dimensions, not outside dimensions.
• Remember that real usable volume may be less due to fittings, dead space, or safety headroom.
• Use fill percentage when you intentionally avoid filling to 100%.
• Be careful with gallon type: US and UK gallons are not the same.

Frequently asked questions

Is litre the same as liter?

Yes. “Litre” and “liter” are the same unit; the spelling depends on regional preference.

Can I use this for solids?

The maths works for any volume, but litres are most commonly used for liquids and container capacity.

Why does calculated tank volume differ from manufacturer specs?

Manufacturers may quote nominal volume, while your measurements may reflect actual internal dimensions or usable fill level. Rounded corners and fittings can also reduce practical capacity.

Bottom line

This litre calculator is designed to be fast and practical: quick unit conversion, rectangular volume, and cylindrical volume in one place. Whether you are planning water storage, evaluating container sizes, or doing everyday metric conversions, it gives dependable results with minimal effort.