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VolumeCalcKitVolume & Capacity Calculators
Tanks & Capacity

Tank Volume Calculator

Calculate water tank volume and liquid capacity in litres, gallons and cubic meters for rectangular, vertical cylindrical and horizontal tanks.

Partial fill calculation
Tank Dimension & Fill LevelLength (L)Dia (D)

50% Liquid Level

Tank Capacity & Fill Results
Decimals:
Current Liquid VolumeLive Output
9,424.78Liters (L)
Additional Computed Dimensions
Max Capacity
18,849.56 L
Fill Level
50% Full
Remaining Liquid Space
9,424.78 L
Equivalent Standard Volume Units
US Gallons (gal)
2,489.76 us_gal
Cubic Meters (m³)
9.42 m3
Cubic Feet (ft³)
332.83 ft3
Imperial Gallons (UK gal)
2,073.16 imp_gal

Mathematical Formula & Step-by-Step Derivation

SI Normalized Math
General Formula:
V_liquid = (r²·arccos((r - d) / r) - (r - d)·√(2rd - d²)) × Length
Live Calculation With Your Input Values:
11. Maximum Tank Capacity
Formula: V_max = π × (D/2)² × L
Substituted: Max Capacity = 18,849.56 L (4,979.53 US gal / 18.85 m³)
Step Result: Max Capacity = 18,849.56 L
22. Current Liquid Volume & Fill Level
Formula: V_liquid = (r²·acos((r-d)/r) - (r-d)√(2rd - d²)) × L
Substituted: Depth = 1 m (50% full)
Step Result: Liquid Volume = 9,424.78 L (2,489.76 US gal)

Remaining space: 9,424.78 L (2,489.76 US gal)

How to Calculate Tank Volume and Water Capacity

How to Calculate Tank Volume

To calculate the volume of a liquid storage tank, identify its geometric shape (vertical cylinder, horizontal cylinder, or rectangular prism), measure internal dimensions, and compute base surface area multiplied by fluid height.

Rectangular Tank Volume

Linear relationship: V = Length × Width × Height. For current water volume, replace total height with current liquid depth.

Vertical Cylindrical Tank Volume

Linear capacity curve: V = π × r² × Height. Volume is directly proportional to liquid fill depth.

Horizontal Cylindrical Tank Volume

Non-linear dip curve: Requires circular segment trigonometry to calculate liquid cross-section area multiplied by tank length.

Tank Volume in Litres & Water Tank Capacity

One cubic meter (m³) of volume contains exactly 1,000 Litres (L). When dimensions are in meters, multiply cubic meters by 1,000 to determine water capacity in litres. If dimensions are in centimeters, divide cubic centimeters by 1,000.

Litres vs Gallons

1 US Liquid Gallon equals 3.78541 Litres (or 1 Liter ≈ 0.26417 US gal). 1 Imperial (UK) Gallon equals 4.54609 Litres (or 1 Liter ≈ 0.21997 UK gal).

Tank Volume Formulas & Partially Filled Mathematics

1. Vertical Cylindrical Tank:

• Total Capacity: V = π × r² × H

• Filled Volume: V_fill = π × r² × d   (d = liquid dip depth)

2. Horizontal Cylindrical Tank (Circular Segment Math):

• Central Angle θ = 2 × arccos((r − d) / r)   [radians]

• Segment Area A = ½ × r² × (θ − sin θ)

• Filled Volume V_fill = A × Length

3. Rectangular Storage Tank:

• Total Capacity: V = Length × Width × Height

• Filled Volume: V_fill = Length × Width × d

Worked Example: Diesel Fuel Dip in a Horizontal Cylinder

Tank Parameters: A horizontal fuel storage tank with diameter 2.0 meters (radius r = 1.0 m) and length 5.0 meters. The dipstick reads a liquid level of 0.6 meters.

1. Total Capacity: π × (1.0 m)² × 5.0 m = 15.7080 m³ (15,708 Liters / 4,149.63 US gal)

2. Central Angle θ: 2 × arccos((1.0 − 0.6) / 1.0) = 2 × 1.1593 = 2.3186 rad

3. Segment Area: ½ × (1.0)² × (2.3186 − sin(2.3186)) = 0.7927 m²

4. Filled Volume: 0.7927 m² × 5.0 m = 3.9635 m³ (3,963.50 Liters / 1,047.05 US gal)

5. Fill Percentage: (3.9635 / 15.7080) × 100% = 25.23% full

Units and Measurement Conversions

Tank DimensionsTypeVolume (m³)Capacity (Liters)Capacity (US Gallons)
Dia 1.0m × H 2.0mVertical Cylinder1.5708 m³1,570.80 L414.96 gal
Dia 2.0m × L 5.0mHorizontal Cylinder15.7080 m³15,707.96 L4,149.63 gal
3.0m × 2.0m × 1.5mRectangular Tank9.0000 m³9,000.00 L2,377.55 gal

Practical Notes & Guidelines

Dip Non-Linearity: Because a horizontal cylindrical tank is widest at the exact middle and narrower at the bottom and top, a 10 cm change in dip level near the bottom represents far less volume than a 10 cm change near the center.

Related Calculators: For standalone cylindrical vessels, see our Cylinder Volume Calculator; for fluid pipes, use the Pipe Volume Calculator; and for aquariums and fish tanks, visit the Aquarium Volume Calculator.

Frequently Asked Questions

How do I calculate tank volume?▼
For a vertical cylindrical tank, multiply π × radius² × height. For a rectangular tank, multiply length × width × height. For a horizontal cylinder, calculate the circular base area multiplied by length.
How do I calculate water tank capacity in litres?▼
Calculate the total internal volume in cubic meters (m³) and multiply by 1,000, since 1 cubic meter equals 1,000 Litres. If dimensions are in centimeters, multiply Length × Width × Height and divide by 1,000.
How many litres does a cylindrical tank hold?▼
Multiply π × (Radius in meters)² × Height in meters × 1,000. For example, a tank with 1 meter radius and 2 meters height holds π × 1² × 2 × 1,000 = 6,283.19 Litres.
How do I calculate a horizontal cylindrical tank volume?▼
Multiply the circular end area (π × radius²) by the total horizontal length (L). For partial liquid levels, use circular segment trigonometry based on the liquid depth.
How do I calculate water volume in a partially filled tank?▼
For rectangular and vertical cylindrical tanks, substitute the current liquid depth for the total height. For horizontal cylindrical tanks, use circular segment math to find the fluid cross-sectional area and multiply by tank length.
What is the difference between tank capacity and current liquid volume?▼
Tank capacity is the maximum total volume the vessel can contain when 100% full. Current liquid volume is the amount of liquid currently stored inside based on the liquid depth reading.
How do I convert tank volume from cubic meters to litres?▼
Multiply cubic meters by 1,000 (1 m³ = 1,000 Liters). For example, a 7.5 m³ tank holds 7,500 Litres of liquid.
How do I convert tank volume to gallons?▼
To convert litres to US liquid gallons, divide by 3.78541 (or multiply cubic meters by 264.172). To convert litres to Imperial UK gallons, divide by 4.54609.
Are US gallons and Imperial gallons the same?▼
No. A US liquid gallon is approximately 3.785 Litres (231 cubic inches), whereas an Imperial (UK) gallon is approximately 4.546 Litres (277.42 cubic inches)—about 20% larger than a US gallon.

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