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Calculate Aquarium Gallons

Updated · Standard formula, shown below

Volume 56.7 US gal
Volume
13,104 cu in
Result
Volume
214.7 L
Result
Length
48 in
You entered

This calculator finds how much water a rectangular aquarium holds. Enter the length, width and height in inches and you get the volume in cubic inches, US gallons and litres.

Formula

Volume = length × width × height. One US gallon is exactly 231 cubic inches; one cubic inch is 0.016387064 L.

  • l, w, h: inside dimensions in inches (cm ÷ 2.54 = inches)

Worked Example

A tank 48 in long, 13 in wide and 21 in high.

  1. 48 × 13 × 21 = 13,104 cu in
  2. 13,104 ÷ 231 = 56.7 US gal
  3. 13,104 × 0.016387 = 214.7 L

Limits and common mistakes

  • Use inside measurements: glass thickness, gravel, rocks and the gap below the rim all reduce the real water volume, often by 10-15%.
  • A UK (imperial) gallon is 277.42 cu in, so the same tank holds 47.2 imperial gallons.
  • Fresh water weighs about 1 kg per litre (8.3 lb per US gallon); check that the stand can carry it.
  • For a tank measured in centimetres, multiply length × width × height and divide by 1000 to get litres directly.
  • A bow-front or corner tank is not a box; this formula overstates its volume.
  • Fill volume matters for dosing water treatments: use the real water volume, not the label size.
Formula used
in l | Length | in | 48 | 0
in w | Width (front to back) | in | 13 | 0
in h | Height | in | 21 | 0
out gal | Volume | US gal | l * w * h / 231 | 1
out ci | Volume | cu in | l * w * h | 0
out lit | Volume | L | ci * 0.016387064 | 1

Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.