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Need Help Calculating Volume


Jul 21, 2004
I have a tank and I am not exactly sure on its capacity. Now I know how to
calculate the volume of simple objects, but this isn't the average rectangluar
aquarium. If you have a look at the pic, you see what I mean. I need to know
the the volume in (US)Gallons so I can be sure this would be suitable for a bimac
and so I can get the corrisponding equipment. :arrow:

Any info or ideas on how to do this would be appreciated.
:grad: Also if you know the answer please explain because
I am curious to know how it is done. Thanks!
the way to work with these tanks, is to approach it geometrically (ah, those classes!):
first, treat the tank as if it is was a square:
26.5 x26.5x18 inches= 55 gallons
next, treat the triangled area the same:
26.5-7.5= 19, so : 19x19x18=28 gallons
subtract 28 from 55 = 22 gallons.
half of the 28 gallons then is added back in: 22 =14 =36 gallons !
This tank is usually sold as a 36 corner...perhaps a little small for a bimac...55's are easier to work with...but good luck!

p.s. sorry for all the edits...figured it first in UK gallons... :|
I think I have found a way to figure it out-
I divided it into 3 sections: A,B, and C


Then I calculated the volume of each individual section... and came up with this:

A- 19” x 7.5” x 18” = 2565 in3
B- 26” x 7.5” x 18” = 3577.5 in3
C- 19” x 19” x 18” = 6498 in3 x 0.5 = 3249 in3

+ 3249.0
9391.5 in3

9391.5 cubic inch = 40.6558442 Gallon (US)

Can anyone second this?

P.s. Thanks for your replies!
just let me throw a spanner in the works too :smile:

You need to take between 10 and 15% off the total for two reasons...

1) a tank is never filled to the very top
2) adding gravel etc displaces water...

so a 40 gal may be 34 gals (US)

As I recall, the US gallon is slighty larger, but I don't know the conversion factor.

its the other way round nancy... An imp is bigger...

According to a bucket of tropic marin... it's big enough for 200 us gals or 165 imp gals (25kg bucket)
there are many good conversion calculators on the internet... type conversion, calculator and the measurements (eg. gallons imperial us litres etc) into google and you should get good results

10 US gallons is roughly 37.9 L!!!!!! We've been sterilising tanks and I've been working out concentrations of Sodium Thiosulphate for neutralising and the quatity is given per 10US gal!!!

Yeah I don't know the formula for converting Cubic Inches into (US)
Gallons- :lol: I get all of my conversions from this handy site:


"Convert just about anything to anything else."

:arrow: Check it out!
It has been really helpful to me,
and I'm sure it could help some of you too!