Choose from 11 industry-standard tank types, enter dimensions in any unit, and get instant results with real-time visualization.
Tank Type
Dimensions
Filled
Volume
Quick Conversions
The tank size calculator works by applying geometry-based volume formulas to the tank dimensions you enter, then converting the result into gallons, liters, cubic feet (ft³), and cubic meters (m³).
To calculate tank size, select 1 of 11 supported tank shapes, enter the tank dimensions in inches (in), centimeters (cm), feet (ft), millimeters (mm), or meters (m), and set the fill percentage. The tank size calculator computes total tank volume, liquid volume, surface area, and water weight in real time.
The tank size calculator supports 5 main categories of tank shapes:
Cylinder Tanks
Vertical and horizontal cylinder tanks use diameter and height to calculate volume. Common for water tank size calculation and fuel tank size calculation.
Rectangular Tanks
Rectangular tanks require length, width, and height. The most common shape for aquarium tank size calculation and fish tank volume calculation.
Oval & Elliptical Tanks
Oval and elliptical tanks use semi-major axis, semi-minor axis, and height. Used for propane tank size calculation and custom water storage.
Capsule Tanks
Capsule tanks combine cylinder volume with hemisphere end caps. Used in pressure vessels and industrial liquid storage.
Cone Tanks
Cone bottom and cone top tanks use top radius, bottom radius, and height. Common for septic tank size calculation and brewery fermentation vessels.
The tank size calculator converts results into 12+ volume units, including US gallons (US gal), Imperial gallons (imp gal), liters (L), milliliters (mL), cubic feet (ft³), cubic inches (in³), cubic centimeters (cm³), cubic meters (m³), and barrels (bbl). The fill level control adjusts liquid volume from 0% to 100%, and the water weight estimation calculates weight in both kilograms (kg) and pounds (lb).
The tank size calculator formula changes based on tank shape. There are 5 core volume formulas used to calculate tank size by dimensions: cylinder, rectangular, oval, capsule, and cone.
Cylinder Tank Formula
Worked Example
A vertical cylinder tank with diameter = 48 inches (121.92 cm) and height = 36 inches (91.44 cm):
Rectangular Tank Formula
Worked Example
A rectangular fish tank with length = 48 in (121.92 cm), width = 13 in (33.02 cm), and height = 21 in (53.34 cm):
This matches a standard 55-gallon aquarium tank size sold by manufacturers like Aqueon and Fluval.
Oval / Elliptical Tank Formula
Worked Example
An oval water tank with semi-major axis = 30 in (76.2 cm), semi-minor axis = 18 in (45.72 cm), and height = 48 in (121.92 cm):
Capsule Tank Formula
Worked Example
A horizontal capsule tank with radius = 12 in (30.48 cm) and cylinder length = 60 in (152.4 cm):
Cone Tank Formula
Worked Example
A cone bottom tank with top radius = 24 in (60.96 cm), bottom radius = 6 in (15.24 cm), and height = 36 in (91.44 cm):
Volume Unit Conversion
To convert cubic inches (in³) to US gallons, divide by 231. To convert cubic inches to liters, divide by 61.024. To convert US gallons to liters, multiply by 3.78541. To convert liters to US gallons, divide by 3.78541.
This tank size comparison chart lists 20 standard tank sizes across aquarium, water, fuel, propane, and septic categories with volume in US gallons and liters.
| Tank Type | Dimensions (L × W × H) | Volume (US Gallons) | Volume (Liters) | Common Use |
|---|---|---|---|---|
| 5-Gallon Aquarium | 16 × 8 × 10 in (40.6 × 20.3 × 25.4 cm) | 5 gal | 18.93 L | Betta fish tank, shrimp tank |
| 10-Gallon Aquarium | 20 × 10 × 12 in (50.8 × 25.4 × 30.5 cm) | 10 gal | 37.85 L | Small freshwater fish tank, guppy tank |
| 20-Gallon Aquarium | 24 × 12 × 16 in (61 × 30.5 × 40.6 cm) | 20 gal | 75.71 L | Community freshwater tank, planted tank |
| 29-Gallon Aquarium | 30 × 12 × 18 in (76.2 × 30.5 × 45.7 cm) | 29 gal | 109.78 L | Cichlid tank, axolotl tank |
| 40-Gallon Breeder | 36 × 18 × 16 in (91.4 × 45.7 × 40.6 cm) | 40 gal | 151.42 L | Reef tank, turtle tank, reptile enclosure |
| 55-Gallon Aquarium | 48 × 13 × 21 in (121.9 × 33 × 53.3 cm) | 55 gal | 208.20 L | Large freshwater tank, saltwater fish tank |
| 75-Gallon Aquarium | 48 × 18 × 21 in (121.9 × 45.7 × 53.3 cm) | 75 gal | 283.91 L | Large reef tank, predator fish tank |
| 90-Gallon Aquarium | 48 × 18 × 24 in (121.9 × 45.7 × 61 cm) | 90 gal | 340.69 L | Saltwater tank, large cichlid tank |
| 125-Gallon Aquarium | 72 × 18 × 21 in (182.9 × 45.7 × 53.3 cm) | 125 gal | 473.18 L | Display reef tank, large freshwater community |
| 180-Gallon Aquarium | 72 × 24 × 25 in (182.9 × 61 × 63.5 cm) | 180 gal | 681.37 L | Professional display tank, marine aquarium |
| Aquarium Sump | 30 × 12 × 16 in (76.2 × 30.5 × 40.6 cm) | 25 gal | 94.64 L | Reef filtration sump, refugium |
| Residential Water Tank | 46 in dia × 48 in H (116.8 × 121.9 cm) | 330 gal | 1,249.19 L | Home rainwater collection, irrigation storage |
| Large Water Storage Tank | 64 in dia × 72 in H (162.6 × 182.9 cm) | 1,000 gal | 3,785.41 L | Agricultural water storage, fire suppression |
| Home Fuel Oil Tank | 44 × 27 × 60 in (111.8 × 68.6 × 152.4 cm) | 275 gal | 1,040.99 L | Residential heating oil storage |
| Vehicle Fuel Tank | Varies by model | 12–36 gal | 45.42–136.27 L | Car, truck, SUV fuel tank |
| 20 lb Propane Tank | 12.5 in dia × 18 in H (31.8 × 45.7 cm) | 4.7 gal | 17.79 L | BBQ grill, portable heater |
| 100 lb Propane Tank | 14.5 in dia × 48 in H (36.8 × 121.9 cm) | 23.6 gal | 89.36 L | Whole-home backup, commercial cooking |
| 500-Gallon Propane Tank | 37.5 in dia × 120 in L (95.3 × 304.8 cm) | 400 gal (80% fill) | 1,514.16 L | Residential propane, home heating |
| Septic Tank (2-Bedroom) | 58 × 46 × 60 in (147.3 × 116.8 × 152.4 cm) | 750 gal | 2,839.06 L | Residential waste, 1–2 bedroom septic system |
| Septic Tank (4-Bedroom) | 96 × 60 × 60 in (243.8 × 152.4 × 152.4 cm) | 1,250 gal | 4,731.76 L | Large residential septic, 3–4 bedroom home |
Aquarium Stocking Guidelines
Aquarium stocking density follows the general rule of 1 inch (2.54 cm) of fish per 1 US gallon (3.79 L) of water for freshwater fish, according to community resources like Aquarium Co-Op and FishLore. Saltwater and reef tanks require 1 inch (2.54 cm) of fish per 5 US gallons (18.93 L) based on recommendations from Reef2Reef. Use stocking calculators like AqAdvisor to verify stocking density based on specific fish species, tank dimensions, and filtration rate.
Tank Weight Estimation
Water weighs 8.34 pounds per US gallon (1 kg per liter). A filled 55-gallon (208.2 L) aquarium weighs 458.7 lb (208.2 kg) of water alone, plus 78–100 lb (35.4–45.4 kg) for the glass tank itself. A filled 125-gallon (473.18 L) aquarium weighs over 1,125 lb (510.3 kg) total. Verify floor load capacity before placing large tanks.
Our calculator uses precise mathematical formulas (up to 15 decimal places of π) and provides results accurate to multiple decimal places. The precision is limited only by the accuracy of your input measurements.
We support 11 tank types: Vertical Cylinder, Horizontal Cylinder, Rectangular, Horizontal Oval, Vertical Oval, Horizontal Capsule, Vertical Capsule, Horizontal Elliptical, Vertical Elliptical, Cone Bottom, and Cone Top. Each uses its own optimized formula for maximum accuracy.
Yes! Each dimension field has its own unit selector supporting millimeters (mm), centimeters (cm), meters (m), inches (in), and feet (ft). All conversions happen instantly without losing any precision.
The fill level slider lets you specify what percentage of the tank is filled (0-100%). The calculator then computes the actual volume of liquid, updates the weight calculation, and the interactive diagram visually shows the water level in real-time.
We provide conversions to: cubic meters, cubic feet, cubic inches, cubic centimeters, liters, milliliters, US gallons, Imperial gallons, barrels, and more. All conversions update in real-time.
Yes, the Tank Size Calculator is completely free to use with no restrictions. There are no ads, no sign-up required, and no limitations on the number of calculations you can perform.