Tank Volume & Substrate Calculator
Work out your tank's water volume, then use the same footprint to figure out how much substrate you'll need to fill it.
Tank Volume Calculator
Enter your tank's internal dimensions in centimetres to work out how much water it holds.
Tank Dimensions
Water Volume
Actual water volume is always a little less than total volume once substrate, decor, and equipment are added — this figure just accounts for not filling all the way to the rim.
Substrate Calculator
Uses the footprint from your tank above to work out how much substrate you'll need at your chosen depth.
Substrate Details
Substrate Needed
Density and bag sizes vary by brand — treat this as a starting estimate and round up when buying, especially for sloped aquascapes.
Getting your numbers right before you buy saves both money and a wasted trip to the shop. This tool works in two steps: first it converts your tank's internal dimensions into a water volume in litres and gallons, then it reuses that same footprint to estimate how much sand, gravel or aqua soil you'll need to reach your chosen substrate depth.
It's built for planning a new setup or reworking an existing one — whether you're stocking a simple flat-bedded community tank or sloping substrate for a full aquascape layout. If you're still deciding on hardscape, plants or a layout style to plan around, the Aquascaping Awards Program and our wider Club Resources are a good next stop, and the Glass Calculator can help if you're building the tank itself rather than just stocking one.
Frequently Asked Questions
Common questions on measuring your tank and estimating substrate accurately.
How do I calculate my aquarium's volume in litres?
Multiply the internal length, width and height of the tank in centimetres, then divide by 1000 to get litres. This gives the total volume to the rim — actual water volume will be a little less once substrate, decor and equipment go in.
Should I measure the inside or outside of the tank?
Always use internal glass measurements rather than the outer dimensions of the cabinet or frame. Glass thickness can otherwise overstate your tank's real water volume, sometimes by several litres on larger tanks.
How much substrate do I need for a planted aquascape?
A flat substrate bed typically needs 2.5–5cm of depth, while a sloped aquascape layout needs 5–8cm at its highest point to hold the slope. Multiply your tank's footprint by the depth to get the volume needed.
What's the difference between sand, gravel and aqua soil for substrate calculations?
Density is the key difference. Sand and gravel are both fairly dense at roughly 1.5–1.6kg per litre, while aqua soil is much lighter at around 0.65kg per litre, so the same depth of aqua soil weighs noticeably less and often comes in smaller bags.
How many litres are in a US gallon and an imperial gallon?
A US gallon is about 3.785 litres, while an imperial gallon (used in South Africa and the UK) is larger at about 4.546 litres. That's why a tank's volume in US gallons and imperial gallons will always be different numbers.
Where can I get help planning a full aquascape or terrarium build?
ECAAC members are happy to help at a club meeting, and our other planning tools can take you further — try the Aquarium Biotope Wizard for a full stocking and layout plan, or the Terrarium Build Wizard if you're planning a terrestrial setup instead.