Aquarium Volume Calculator — Litres & Gallons of Your Tank

← Research ReefThe Creative Island · Island 13

How much water is really in there? Rectangular and cylinder tanks, litres and gallons, honest about the air gap at the top.

Tank shape Rectangular Cylinder

Length (cm)

Width (cm)

Height (cm)

Diameter (cm) — cylinder only

Fill level: 90% (water never reaches the rim)

How to use this tool

1. Choose your tank shape: rectangular or cylinder.
2. Measure in cm: length × width × height (or diameter × height).
3. Set the fill level — water always sits below the rim — and read litres and gallons.

Example

A standard 60 × 30 × 35 cm tank: gross 63 L, at 90% fill ≈ 56.7 L — and with a gravel bed and wood, realistically a ~48 L working volume. That's the number your stocking and dosing decisions should use.

The formula

rectangular: L×W×H ÷ 1000 = litres  |  cylinder: π×(D÷2)²×H ÷ 1000

What the result means

Two mistakes ruin tank math: quoting the gross volume (nobody fills to the rim) and ignoring displacement (gravel, wood and filter media replace water). Dosing medication or fertilizer by the gross figure overdoses a smaller real volume — this calculator nudges you toward the honest number.

Frequently asked questions

Why does the tank shop say 60L but this says 56?

Shops quote gross (or marketing) volume. Real water level, glass thickness and decor take 10–20% away — always dose by actual litres.

How do I account for a sump or canister filter?

Add the filter's water volume (sump water depth × area, or ~2–4 L for a typical canister) to the tank's figure for total system volume.

Does shape affect stocking?

Yes — surface area matters more than litres for gas exchange; a long shallow 60L outperforms a tall narrow 60L. Volume is necessary math, not the whole story.

Is my tank data uploaded?

No — computed locally in your browser.

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Explore the island world

• Research Reef — the island where this tool lives.
• The Main Island — drive the boat, explore the whole world.
• The 90s Kids Island — where most of us started.

Privacy & data: this tool runs entirely in your browser — nothing you type is uploaded, saved or sent anywhere. · Disclaimer: calculations use standard scientific formulas — for lab, safety or field decisions, always double-check with official protocols. · Privacy Policy · Disclaimer