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DIY Cost Tools

DIY Cost Tools

Aquarium Volume Calculator

Estimate the filled water volume and water weight of a rectangular aquarium from interior dimensions and fill percentage.

Use consistent units exactly as labeled. Decimal and scientific notation are accepted for non-integer fields; blanks, commas, fractions and non-finite entries are rejected.

Filled volume9331.2 in³
US gallons40.39480519 gal
Liters152.9109716 L
Approximate water weight337.1109689 lb

The displayed results apply to the default example. Enable JavaScript to calculate other inputs.

How to use this calculator

  1. Replace the example values with your own measurements, schedule, prices, or media settings.
  2. Keep each value in the unit printed beside its field.
  3. Select Calculate and review every result together with the assumptions below.

Formula and method

Filled cubic inches = length × width × water height × fill percentage. US gallons = cubic inches ÷ 231; liters = gallons × 3.785411784.

Calculations run in your browser. Results are hidden whenever an input changes or validation fails, preventing an old answer from being mistaken for the current calculation.

Worked example

Interior length = 36 in; Interior width = 18 in; Interior water height = 16 in; Fill percentage = 90 %. The calculator returns Filled volume = 9331.2 in³; US gallons = 40.39480519 gal; Liters = 152.9109716 L; Approximate water weight = 337.1109689 lb.

The worked example uses the same default values shown in the interface, so the displayed result and explanation can be checked directly.

Limitations

Use interior water dimensions, not exterior tank dimensions. Substrate and décor displace water. Total system weight also includes glass, stand, equipment, rock and substrate; use a stand rated for the complete load.

Use the result as a planning estimate. Confirm prices, policies, equipment ratings, units and professional requirements that apply to your situation.

Frequently asked questions

Why is the real water volume usually lower?

Glass thickness, freeboard, substrate, rocks, decorations and equipment reduce the volume available to water.

Why does the calculator reject my entry?

Each field shows its supported range. Whole-number fields reject decimals, and all fields reject blanks, words, comma-formatted numbers, fractions and non-finite values.

How should I round the result?

Keep extra digits while planning, then round to the precision supported by your inputs, package sizes, billing rules or equipment settings.

Review notes and reference

Reviewed October 4, 2026. The formula was checked against the displayed worked example. The script was tested for defaults, field boundaries, invalid formats, condition-specific errors and recovery after an error. Reference: How Our Calculators Work. Explanations and examples are original.

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