Tank Volume Calculator
Calculate tank volume for cylinders, rectangles, and spheres. Shows gallons, liters, cubic feet, and barrels. Supports partial fill levels.
Estimates only. Always verify quantities with a professional before purchasing materials. Building projects must comply with local codes and regulations.
About Tank Volume Calculator
This tank volume calculator determines the capacity of tanks in four common shapes: vertical cylinder, horizontal cylinder, rectangular, and spherical. Enter dimensions in feet, inches, or metres and get volume in US gallons, imperial gallons, litres, cubic feet, cubic metres, and barrels. A partial fill slider shows how much liquid is in the tank at any fill level.
Volume Formulas by Tank Shape
| Shape | Formula | Variables |
|---|---|---|
| Vertical cylinder | V = pi x r² x h | r = radius, h = height |
| Horizontal cylinder | V = pi x r² x L | r = radius, L = length |
| Rectangular | V = L x W x H | L = length, W = width, H = height |
| Sphere | V = (4/3) x pi x r³ | r = radius |
All results are first calculated in cubic feet (or cubic metres), then converted to gallons and litres using the standard conversion factors.
Volume Unit Conversions
| From | To | Multiply By |
|---|---|---|
| 1 cubic foot | US gallons | 7.4805 |
| 1 cubic foot | Imperial gallons | 6.2288 |
| 1 cubic foot | Litres | 28.3168 |
| 1 US gallon | Litres | 3.7854 |
| 1 Imperial gallon | Litres | 4.5461 |
| 1 barrel (oil) | US gallons | 42 |
| 1 cubic metre | Litres | 1,000 |
Common Tank Sizes
| Application | Typical Shape | Typical Size | Capacity |
|---|---|---|---|
| Home water heater | Vertical cylinder | 20 in dia x 50 in tall | 40-50 US gallons |
| Residential water storage | Vertical cylinder | 4 ft dia x 6 ft tall | ~560 US gallons |
| Propane tank (residential) | Horizontal cylinder | 3.5 ft dia x 10 ft long | ~500 US gallons |
| Above-ground oil tank | Horizontal cylinder | 2.5 ft dia x 5 ft long | ~275 US gallons |
| Fish tank / aquarium | Rectangular | 4 ft x 1 ft x 1.5 ft | ~45 US gallons |
| Rain barrel | Vertical cylinder | 23 in dia x 34 in tall | ~55 US gallons |
| IBC tote | Rectangular | 40 x 48 x 46 in | 275 US gallons (standard) |
Partial Fill Mode
The fill percentage slider lets you estimate how much liquid is in a partially filled tank. This is useful for checking current levels, planning delivery schedules, or calculating remaining capacity. The display shows filled volume alongside total capacity.
| Fill Level | Volume (500 gal tank) | Common Scenario |
|---|---|---|
| 100% | 500 gallons | Just filled / delivered |
| 75% | 375 gallons | Normal operating level |
| 50% | 250 gallons | Time to plan a refill |
| 25% | 125 gallons | Schedule delivery soon |
| 10% | 50 gallons | Urgent - order immediately |
For horizontal cylinders, the relationship between fill height and volume is not linear - a tank that looks half-empty by sight line may actually hold more or less than 50% depending on the liquid level relative to the radius.
Water Storage Planning
| Use | Daily Water Need (per person) | Family of 4 (weekly) |
|---|---|---|
| Drinking and cooking | 1-2 gallons | 28-56 gallons |
| Basic hygiene | 5-10 gallons | 140-280 gallons |
| Full household use | 50-100 gallons | 1,400-2,800 gallons |
| Emergency backup (3 days) | 1 gallon minimum | 12 gallons minimum |
Choosing a Tank Shape
| Shape | Advantages | Common Uses |
|---|---|---|
| Vertical cylinder | Small footprint, easy to read level gauges | Water storage, water heaters, rain collection |
| Horizontal cylinder | Low profile, stable on trailers | Fuel storage, propane, transport tanks |
| Rectangular | Space-efficient, stackable | Aquariums, IBC totes, custom-built tanks |
| Sphere | Maximum volume for surface area, even pressure distribution | LPG storage, industrial pressure vessels |
For bulk material volumes (gravel, mulch, soil), the cubic yards calculator converts area measurements to cubic yards. For general geometric volume calculations, the volume calculator covers additional shapes like cones and pyramids. All calculations run in your browser with no data stored.
Frequently Asked Questions
How do I calculate the volume of a cylindrical tank?
Multiply pi (3.14159) by the radius squared, then multiply by the height. For a tank 4 feet in diameter and 6 feet tall, the volume is 3.14159 x 2 x 2 x 6 = 75.4 cubic feet, which equals about 564 gallons.
How many gallons are in a cubic foot?
One cubic foot holds 7.48 US gallons. To convert cubic feet to gallons, multiply by 7.48. One cubic foot also equals about 28.32 liters.
How do I calculate a partially filled tank?
For a simple estimate, calculate the full tank volume and multiply by the fill percentage. For example, a 500-gallon tank at 75% holds about 375 gallons. Use the fill level slider in this calculator for quick partial volume estimates.
What is the difference between US gallons and imperial gallons?
One US gallon equals about 3.785 liters, while one imperial gallon equals about 4.546 liters. An imperial gallon is about 20% larger than a US gallon. This calculator shows both units.
How big of a water tank do I need for my house?
For a typical residential backup water supply, a 200-500 gallon tank is common. For full off-grid use, plan for 50-100 gallons per person per day. A family of four using 80 gallons each would need at least a 320-gallon daily supply.
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