Backyard Aquaponics
A place to discuss aquaponics

If you buy a 250gl IBC and cut the top off to make GB. How do you know after filling it up how much water is in it?

It all depends...

But to help you figure this out. Here are some helpful guidelines:
1) The "275 gallon" IBCs are usually 48"x40" on its base and 46" on its height. (cage size)
2) The "330 gallon" IBCs are usually 48"x40" on its base and 53" on its height. (cage size)

And 1 Cubic Foot = 7.48 US Gallons

So , with IBCs we can assume: 8.25 Gallon per inch...

12" grow bed = 99 Gallons
13" grow bed = 108 Gallons
14" grow bed = 116 Gallons

But this is a full square inch/foot so round the number down to 8 Gallon per inch for the curved sides and the cage .

measure it -
Length x width x depth

Darn I really wish we used metric system ... 1 gallon = 1000 cubic inches. One day someone will switch us over.

Edit: just encase you don't know... it doesn't.

Thanks so much for the info.

Up the front side are markings in metric and imperial, metric markings are every 100 litres.

My apologies for resurrecting an old thread....but the math doesn't appear correct. You are saying 8.25 gallons per inch. And also saying a 275 gal IBC is 46" high. 46 x 8.25 would equal 379.5 gallons!

Shouldn't the math be: take the total volume and divide by the height to give gallons per inch? (this would be just a little over 5.9 gpi for the 275 and 6.2 gpi for the 330 gal IBC) As the width and depth are the same (only the height is different) I'm assuming the differences are in errors in the measurement of the height. So averaging these would result in about 6 gpi... or am I missing something?

These markings of course don't work upside down.
But the math remains the same
Length x hight x width equals cubic *
* being what ever type of measure you are using.