Volume Calculator
Calculate the volume of cylinders, rectangular tanks, round tanks, oval containers, and pipes. Get results instantly in gallons, liters, cubic feet, cubic meters, and more.
Cylinder Volume Formula
This cylinder volume calculator finds the volume of cylinders, rectangular tanks, oval containers, and pipes — giving you instant results in gallons, liters, cubic feet, and cubic meters. Whether you need a tank capacity calculation for a water storage project or a precise scientific measurement, this tool handles it all with step-by-step working.
You can also express this using diameter: V = p × (d/2)² × h. If you measure across the full circle (the diameter), divide by 2 to get the radius before using the formula.
How to Calculate the Volume of a Cylinder
Follow these six steps to calculate cylinder volume accurately:
- Step 1: Measure the radius of the circular base. If you have the diameter, divide it by 2.
- Step 2: Measure the height (or length for a horizontal cylinder).
- Step 3: Square the radius: r² = r × r
- Step 4: Multiply by p (3.14159265…)
- Step 5: Multiply by the height: V = p × r² × h
- Step 6: Convert to your desired unit (gallons, liters, etc.)
Example 1: Swimming Pool (Circular)
Radius = 4 m, Depth = 1.5 m
- r² = 4² = 16
- p × 16 = 50.2655
- V = 50.2655 × 1.5 = 75.398 m³
- = 75,398 L = 19,908 US gallons
Example 2: Water Bottle
Radius = 3.5 cm, Height = 20 cm
- r² = 3.5² = 12.25
- p × 12.25 = 38.485
- V = 38.485 × 20 = 769.69 cm³
- = 769.69 mL ˜ 0.77 L
Example 3: Storage Tank
Diameter = 6 ft, Height = 8 ft ? Radius = 3 ft
- r² = 3² = 9
- p × 9 = 28.274
- V = 28.274 × 8 = 226.19 ft³
- = 226.19 × 7.48052 = 1,691.6 US gallons
How to Calculate Tank Capacity in Gallons
To convert any volume in cubic feet to US gallons, multiply by 7.48052. This works for rectangular tanks, cylindrical tanks, and any other shape.
Example 1: Rectangular Fish Tank
4 ft × 2 ft × 2 ft
- V = 4 × 2 × 2 = 16 ft³
- Gallons = 16 × 7.48052 = 119.7 US gallons
Example 2: Cylindrical Water Tank
Diameter = 4 ft ? radius = 2 ft, Height = 5 ft
- V = p × 2² × 5 = 62.83 ft³
- Gallons = 62.83 × 7.48052 = 470.1 US gallons
Example 3: Square Hot Tub
6 ft × 6 ft × 3 ft
- V = 6 × 6 × 3 = 108 ft³
- Gallons = 108 × 7.48052 = 807.9 US gallons
How many gallons in a square foot?
Answer: 1 square foot of floor area filled to 1 foot depth = 7.48 US gallons. To find gallons: multiply your square footage by the depth in feet, then multiply by 7.48052.
Volume of a Rectangle and Square Box
A rectangular box (cuboid) has volume = Length × Width × Height. A square box (cube) has all three dimensions equal, so V = s³.
Example 1: Shipping Box
60 cm × 40 cm × 30 cm
- V = 60 × 40 × 30 = 72,000 cm³
- = 72 liters
Example 2: Cube Storage Unit
50 cm × 50 cm × 50 cm
- V = 50³ = 125,000 cm³
- = 125 liters
Volume Units Conversion Reference
| From | To Liters | To US Gallons | To UK Gallons | To ft³ | To m³ |
|---|---|---|---|---|---|
| 1 m³ | 1,000 | 264.172 | 219.969 | 35.3147 | 1 |
| 1 ft³ | 28.3168 | 7.48052 | 6.22884 | 1 | 0.028317 |
| 1 US gallon | 3.78541 | 1 | 0.832674 | 0.133681 | 0.003785 |
| 1 UK gallon | 4.54609 | 1.20095 | 1 | 0.160544 | 0.004546 |
| 1 L | 1 | 0.264172 | 0.219969 | 0.035315 | 0.001 |
| 1 cm³ | 0.001 | 0.000264 | 0.000220 | 0.0000353 | 0.000001 |
Worked Examples
How to find the volume of a cylinder step by step
Use V = p × r² × h. Measure the radius and height, square the radius, multiply by p, then multiply by height. Example: r = 5 cm, h = 12 cm ? V = p × 25 × 12 = 942.48 cm³ = 0.942 L.
How to calculate volume of a cylindrical tank in gallons
Find volume in cubic feet using V = p × r² × h (all in feet), then multiply by 7.48052. Example: diameter 3 ft, height 4 ft ? r = 1.5 ft ? V = p × 2.25 × 4 = 28.27 ft³ × 7.48052 = 211.5 US gallons.
How to find cubic feet of a cylinder
Measure radius and height in feet. Apply V = p × r² × h. Example: r = 2 ft, h = 6 ft ? V = p × 4 × 6 = 75.40 ft³.
How to find the volume of a tube or pipe
Calculate the inner diameter: ID = OD - 2 × wall thickness. Then V = p × (ID/2)² × length. Example: OD = 4 in, wall = 0.25 in, length = 120 in ? ID = 3.5 in ? V = p × 3.0625 × 120 = 1,154.5 in³ = 5.0 US gallons.
How to calculate volume of an oval tank
Use V = p × a × b × h where a and b are the semi-axes of the oval cross-section. Example: a = 2 ft, b = 1.5 ft, h = 4 ft ? V = p × 2 × 1.5 × 4 = 37.70 ft³ = 282.0 US gallons.
How to measure a tank in gallons
Measure all dimensions in feet. Calculate volume in ft³ using the appropriate formula for your tank shape. Multiply cubic feet by 7.48052 to get US gallons. Example: rectangular 5 ft × 3 ft × 2 ft = 30 ft³ = 224.4 US gallons.
How many gallons does a cylinder hold?
Calculate V = p × r² × h in cubic feet, then multiply by 7.48052. Example: 55-gallon drum has diameter ~23 in (r = 11.5 in = 0.958 ft), height 33.5 in (2.792 ft) ? V = p × 0.918 × 2.792 = 8.05 ft³ × 7.48052 = 60.2 gallons.
How to convert m³ to gallons
Multiply cubic meters by 264.172 to get US gallons, or by 219.969 for UK gallons. Example: 2.5 m³ × 264.172 = 660.4 US gallons.
How to find the volume of a rectangular water tank
V = Length × Width × Height. Convert to liters: multiply m³ by 1000. Example: 1.2 m × 0.8 m × 0.6 m = 0.576 m³ = 576 liters = 152.2 US gallons.
How to calculate the capacity of a round tank
A round (cylindrical) tank uses V = p × r² × h. For a tank with diameter 10 ft standing 8 ft tall: r = 5 ft ? V = p × 25 × 8 = 628.3 ft³ = 4,700 US gallons.