On This Page
- How to use the Rectangular Tank Volume Calculator
- Rectangular tank volume formula
- How to calculate rectangular tank volume
- How to calculate liquid volume in a rectangular tank
- Liters, litres, and gallons
- Worked examples
- Rectangular tank volume units
- Frequently asked questions
How to Use the Rectangular Tank Volume Calculator
Use this rectangular tank volume calculator when you need full tank capacity or the amount of liquid currently inside. Enter length, width, height, and filled depth, and the page shows fill percentage, liters, US gallons, imperial gallons, cubic feet, and steps.
Use it for water tanks, aquariums, rectangular fuel tanks, storage containers, sumps, pools, classroom geometry problems, and any tank shaped like a rectangular prism.
Rectangular Tank Volume Formula
The standard formula for calculating full rectangular tank volume is:
- V = full tank volume
- l = inside length
- w = inside width
- h = inside height
A rectangular tank is a rectangular prism, so its volume is found by multiplying the three inside dimensions.
How to Calculate Rectangular Tank Volume
To calculate the volume of a rectangular tank by hand, measure the inside length, inside width, and inside height. Make sure all three values use the same unit before multiplying.
Step 1: Measure Length, Width, and Height
Use inside measurements if you need capacity. For a real tank, the outside dimensions are not always the same as the usable internal space.
Step 2: Multiply Length by Width
This gives the rectangular base area.
Step 3: Multiply by Height
Multiplying base area by height gives the full three-dimensional volume.
- Find inside length: l
- Find inside width: w
- Find inside height: h
- Multiply l × w × h
- Write the answer in cubic units
How to Calculate Liquid Volume in a Rectangular Tank
Liquid volume uses filled depth instead of full tank height. This answers questions like "how much water is currently in the tank?"
If the tank is full, filled depth equals tank height. If the tank is half full, filled depth is half of the inside height.
Rectangular Tank Volume in Liters, Litres, and Gallons
Many practical tank questions need capacity in liters, litres, or gallons instead of cubic units. The calculator above converts the filled volume automatically.
- 1 m³ = 1,000 liters
- 1,000 cm³ = 1 liter
- 231 in³ = 1 US gallon
- 1 ft³ ≈ 7.48052 US gallons
Worked Rectangular Tank Volume Examples
These examples focus on the difference between full tank capacity and the amount of liquid currently in the tank. That one detail changes which height you use.
Example 1: Calculate Volume of Water in a Rectangular Tank
Problem: A rectangular water tank has inside dimensions of 3 m long, 1.5 m wide, and 1.2 m high. The water level is 0.8 m deep. How much water is in the tank?
- Full capacity = 3 × 1.5 × 1.2 = 5.4 m³
- Current water volume = 3 × 1.5 × 0.8 = 3.6 m³
- Convert to liters: 3.6 × 1,000 = 3,600 L
- Fill percentage = 3.6 ÷ 5.4 = 66.7%
Answer: The tank currently contains 3.6 m³, or 3,600 liters, of water.
Example 2: Rectangular Tank Volume Calculator in Litres
Problem: A small treatment tank is 120 cm long, 60 cm wide, and 50 cm high. It is filled to 35 cm. Calculate the liquid volume in litres.
- Filled volume = 120 × 60 × 35 = 252,000 cm³
- Convert cm³ to litres: 252,000 ÷ 1,000 = 252 L
- Full capacity = 120 × 60 × 50 = 360,000 cm³ = 360 L
Answer: The tank currently holds 252 litres and has a full capacity of 360 litres.
Example 3: Rectangular Tank Volume in Gallons
Problem: An aquarium has inside dimensions of 36 inches long, 18 inches wide, and 16 inches high. Estimate the full capacity in US gallons.
- Volume = 36 × 18 × 16 = 10,368 in³
- US gallons = 10,368 ÷ 231 = 44.88 gal
- Leave space at the top for equipment, air, and water movement.
Answer: The aquarium holds about 44.9 US gallons when filled to the top.
Example 4: Rectangular Fuel Tank Volume
Problem: A rectangular fuel tank has inside dimensions 5 ft by 3 ft by 2 ft. It is filled to a depth of 1.4 ft. Find the current liquid volume in cubic feet.
- Full tank volume = 5 × 3 × 2 = 30 ft³
- Current liquid volume = 5 × 3 × 1.4 = 21 ft³
- Fill percentage = 21 ÷ 30 = 70%
Answer: The tank currently contains 21 ft³ of liquid.
Example 5: Find Filled Depth From Liquid Volume
Problem: A rectangular tank is 2 m long and 1 m wide. It contains 1.2 m³ of water. What is the filled depth?
- Use filled depth = liquid volume ÷ (length × width)
- filled depth = 1.2 ÷ (2 × 1)
- filled depth = 0.6 m
Answer: The water is 0.6 meters deep.
Rectangular Tank Volume Units
Rectangular tank volume is written in cubic units, while liquid capacity is commonly reported in liters or gallons.
| Input Unit | Volume Unit | Useful Conversion |
|---|---|---|
| Centimeters | cm³ | 1,000 cm³ = 1 liter |
| Meters | m³ | 1 m³ = 1,000 liters |
| Inches | in³ | 231 in³ = 1 US gallon |
| Feet | ft³ | 1 ft³ ≈ 7.48052 US gallons |
Rectangular Tank Volume Mistakes to Avoid
- Using outside dimensions: Inside dimensions give better capacity estimates.
- Confusing height and filled depth: Height is full tank height; filled depth is current liquid level.
- Mixing units: Convert all measurements before multiplying.
- Using this formula for round tanks: Cylindrical and capsule tanks need different formulas.
- Ignoring freeboard: Real tanks may need empty space at the top for safety or operation.
Frequently Asked Questions
How do you calculate rectangular tank volume?
Use V = length × width × height. Use inside dimensions if you are calculating capacity.
How do you calculate volume of liquid in a rectangular tank?
Use liquid volume = length × width × filled depth. Filled depth is the current liquid level.
How do you calculate rectangular tank volume in litres?
If dimensions are in centimeters, multiply length × width × filled depth, then divide by 1,000 to get litres.
How do you calculate rectangular tank volume in gallons?
If dimensions are in inches, calculate cubic inches first, then divide by 231 to get US gallons.
Should I use inside or outside tank dimensions?
Use inside dimensions for liquid capacity. Outside dimensions include tank walls and can make the answer too large.