RevenueLab.fyi
Revenue Rex logo mark
🧰 Other · Rex's Toolbox

Aquarium Volume & Stocking Calculator

Gallons, water weight, heater wattage, and filter turnover.

Revenue Rex peeking

Rex says

Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.

Try a scenario

Click to load — tweak from there.

Inputs

Result

Actual water volume (gal)

48.6

Gross volume (gal)

54.0

Liters

184.0

Filled weight (lb)

514

Recommended heater (W)

200

Filter flow needed (GPH)

292

25% water change (gal)

12.2

Revenue Rex peeking

Psst — share this and help Rex grow

One click, a permanent link with your numbers baked in.

More other

How to use this

  1. 1Enter length (in).
  2. 2Enter width (front to back) (in).
  3. 3Enter water height (in).
  4. 4Enter substrate & decor displacement (%).
  5. 5Enter degrees above room temp (°F).
  6. 6Enter target filter turnover (×/hr).
  7. 7Read your actual water volume (gal) on the right — it updates as you type.
  8. 8Hit Share to keep the scenario or send it to someone.

About this calculator

Tank labels are nominal — a '55 gallon' holds noticeably less once you account for glass thickness, substrate, and rock. Compute true water volume from your dimensions, then size the heater and filter off that real number.

FormulaGallons = (L × W × H in inches) ÷ 231, minus displacement; heater ≈ 3–5 W per gallon.

Worked example

Using the values the calculator loads with:

Inputs

  • Length: 48 in
  • Width (front to back): 13 in
  • Water height: 20 in
  • Substrate & decor displacement: 10 %
  • Degrees above room temp: 8 °F
  • Target filter turnover: 6 ×/hr

Results

  • Actual water volume (gal): 48.6
  • Gross volume (gal): 54
  • Liters: 184
  • Filled weight (lb): 514
  • Recommended heater (W): 200
  • Filter flow needed (GPH): 292
  • 25% water change (gal): 12.2

What each field means

Inputs

Length (in)
The length used in the calculation, measured in in. Starts at 48 in so you have a working example on load.
Width (front to back) (in)
The width (front to back) used in the calculation, measured in in. Starts at 13 in so you have a working example on load.
Water height (in)
The water height used in the calculation, measured in in. Starts at 20 in so you have a working example on load.
Substrate & decor displacement (%)
The substrate & decor displacement used in the calculation, measured in %. Starts at 10 % so you have a working example on load. Accepted range: 0–40 %.
Degrees above room temp (°F)
The degrees above room temp used in the calculation, measured in °F. Starts at 8 °F so you have a working example on load. Accepted range: 0–30 °F.
Target filter turnover (×/hr)
The target filter turnover used in the calculation, measured in ×/hr. Starts at 6 ×/hr so you have a working example on load. Accepted range: 1–20 ×/hr.

Results

Actual water volume (gal)
Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
Gross volume (gal)
Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
Liters
Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
Filled weight (lb)
Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
Recommended heater (W)
Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
Filter flow needed (GPH)
Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
25% water change (gal)
Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.

FAQ

Why is my tank lighter than 8.34 lb per gallon?

It is heavier, not lighter — glass, substrate, and rock add on top of water weight. A 55-gallon setup lands near 600 pounds, which is more than many floors and stands are rated for without spreading the load.

Is more filter flow always better?

For most community freshwater tanks, 4–6× turnover is plenty. Reef tanks want 10× or more, while bettas and fry need flow deliberately reduced.

Accuracy and limitations

  • Estimates assume standard, average conditions — local rules, pricing, and materials vary.
  • Results are rounded for readability; add a buffer before ordering, booking, or committing.
  • Double-check anything with a real cost attached against a local quote.

Related tools

Pet Ownership Cost Calculator

Total first-year and lifetime cost of a dog or cat.

Cite this calculator

Writing about this topic? Grab a citation — every link helps keep these tools free.

APA
RevenueLab. (2026). Aquarium Volume Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/aquarium-volume
HTML
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/aquarium-volume" target="_blank" rel="noopener">Aquarium Volume Calculator — RevenueLab</a> (2026).</p>
Markdown
Source: [Aquarium Volume Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/aquarium-volume) (2026).
Advertisement