# Aquarium Volume Calculator (I bet your tank ain't as big as you think it is)

dan200
SIZE MATTERS

So, I bought a craigslist tank and stand combo and I thought I was buying a 130 gallon tank. NOPE

I have been calling it a 6 ft x 1 1/2 ft x 2 ft because that's what the ad said and, well it isn't.

I was taking some measurements today so I can begin to design a new stand and canopy for my big glass box and here's what happened.

The rI'm (or ring or whatever) on the top and bottom actually measures 72.5 in long x 18.5 in deep and 23.5 in high. and the perimiter of the glass is of course, slightly smaller than that. This made me curious so, I went on to calculate the actual interior dimensions which ended up being 71.5 in x 17.25 in deep and 22 in tall.

I plugged those numbers (the actual interior dimensions) into the a fish tank volume calculator and it tells me that my actual interior volume is 117.46 gallons. Not the 130 I thought I had.

LINKY FOR VOLUME CALCULATOR (it does both US gallons/inches and liters/centimeters)
>

I'm not mad or anything but I did find it interesting.

The good part of all this now I know and can properly portion whatever "x per gallon" calculation I need to do. And by adjusting the height by reducing it by an inch on that calculator at the link I posted I calculated that every inch of water in my tank is 5.33 gallons. This info will prove to have some value when I do partial water changes.

If I want to get even more precise, I can use the same calculator to figure out how much volume my rock/substrate take up (by seeing how much water they displace) and also find the actual volume of water my canister and whatever plumbing and sump system I eventually put on my set up are.

Ive read a little bit of this forum trying to learn stuff (I'm new here) and have yet to come across anyone who actually said they did these calculations on their tank(s). Not to say anyone hasn't. But we all (me included) seem to regularly call our tanks volume by what we think it is instead of what it actually is.

ryanr
Hi,
Welcome to Fishlore

What you've encountered is not uncommon - many don't think about the volume lost due to the glass thickness.

The industry still refers to tank dimensions and volumes based on outer dimensions, and it's still correct, just that some of the volume capacity happens to be glass.

Take a 20G High for example, 24" x 12" x 16", or 61cm x 30.5cm x 40.5
The volume of that is 19.95G, or 74.23 litres

Now, the average 20G is made from 6mm glass, meaning true dimensions are 60.4 x 29.9 x 39.9cm, 72 litres, 19G.

And then, when you starting adding substrates etc, the actual water in your tank may be significantly less. I reckon my 20G is closer to 12 or 13G of actual water in the system.

But we still generally buy our equipment based on the total outside dimension - a little extra filtration is always handy

jdhef
LINKY FOR VOLUME CALCULATOR (it does both US gallons/inches and liters/centimeters)
>

If you scroll all the way to the bottom of this page (or any other page on FishLore) there should be a tank size calculator, Temperature converter (F to C and C to F) and a gallons to liter converter and vise versa

dan200
If you scroll all the way to the bottom of this page (or any other page on FishLore) there should be a tank size calculator, Temperature converter (F to C and C to F) and a gallons to liter converter and vise versa

LyleB
Thanks for this post. I, to, have found a wide variance in stated sizes and actual. I decided to just go with the conventionally accepted volumns when talking about the standard tanks, but not all my tanks fit into the standard dimensions. For these, I usually refer to actual volumn, as measured internally, like you have done.

About the calculators, don't feel bad, it took me a while to notice them as well.

Welcome to Fishlore.

freebie
Thanks for posting very interesting subject

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