Tank Volume Calculator
Calculate the capacity of a tank in gallons, liters, and cubic feet. Supports vertical and horizontal cylinders and rectangular tanks, with partial-fill volume.
1 cubic foot = 7.48 gallons | 231 cubic inches = 1 gallon
Tank Capacity Calculator
Rectangular Tank Gallons Chart (Common Sizes)
To find gallons in a rectangular tank, multiply length × width × height in inches, then divide by 231. For example, a 24 × 12 × 12 inch tank holds about 15 gallons. The chart below covers common tank and aquarium dimensions.
| Dimensions (L×W×H, in) | US Gallons | Liters |
|---|---|---|
| 24 × 12 × 12 | 15.0 | 57 |
| 24 × 16 × 12 | 19.9 | 76 |
| 30 × 12 × 12 | 18.7 | 71 |
| 36 × 18 × 18 | 50.5 | 191 |
| 48 × 13 × 21 | 56.7 | 215 |
| 48 × 18 × 21 | 78.5 | 297 |
| 48 × 24 × 24 | 119.7 | 453 |
| 72 × 18 × 24 | 134.6 | 510 |
Tank Volume Formulas
Cylinder
V = π × r² × L
r = radius, L = length or height. Works for vertical and horizontal cylinders.
Rectangular
V = L × W × H
Length × width × height, all in the same unit.
Convert to Gallons
gal = in³ ÷ 231
Or cubic feet × 7.48. Liters = in³ × 0.01639.
Frequently Asked Questions
How do I calculate how many gallons my tank holds?
Measure the tank in inches, calculate its volume in cubic inches, then divide by 231. For a rectangular tank, volume = length × width × height. For a cylinder, volume = π × radius² × length. Dividing cubic inches by 231 gives US gallons; divide cubic inches by 61.02 for liters.
How many gallons is a 24x12x12 tank?
A 24 × 12 × 12 inch tank holds about 15 gallons (24 × 12 × 12 = 3,456 cubic inches ÷ 231 = 14.96 gallons). This is the standard "15-gallon" aquarium size.
How many gallons is a 48x24x24 tank?
A 48 × 24 × 24 inch tank holds about 120 gallons (27,648 cubic inches ÷ 231 = 119.7 gallons). This corresponds to a standard 120-gallon aquarium or storage tank.
How many gallons are in a cubic foot?
One cubic foot holds 7.48 US gallons. So to convert cubic feet to gallons, multiply by 7.48. A tank measuring 10 cubic feet holds about 74.8 gallons.
How do you find the volume of a partially filled tank?
For a vertical cylinder or rectangular tank, the fill volume is proportional to the liquid depth — multiply the full volume by (fill height ÷ total height). A horizontal cylinder is trickier because the cross-section is a circular segment; this calculator handles that automatically when you enter a fill level.