how many oscar can i put in a 3ft tank?

welcome to the site

you will have to give us the exact dimensions of your tank, or if you know how many gallons it holds before we can give you any advice

It depends on the height and width. If it is tall (2ft) and has enough depth (2ft) then 1 oscar, else none

36 by 16 by 16 (all in inches)

I think that's 33.22 UK gallons.
Advised tanksize for one Oscar is 55 Gallons...
So, I'm affraid your tank is not big enough only for one Oscar!
Don't mean to spoil the party.

55gallon for 1 oscar that is how big? and what if i put it in a 36 by 16 by 16 tank it will grow to a certain size or it will continue to grow bigger?

It will either have stunted growth or just keep growing.
Problem is gonna be the bioload in your tank.
Oscars produce a lot of waist and will suffer from that.
A fullgrown O can become say 15 ", and will need space to swim.
Keeping it in a small tank will be like keeping a dog in a bench for all it's life.
Your fish won't go on holidays but will spent his entire life in that tank!!!
Think it'd be best to get a bigger tank before getting an O, or else your fish may suffer and/or die!

so you are trying to say that a 55 gallon tank for one fully grown oscar(15 inch)?

Yes, and mind you they grow very fast.
Mine went passed the 10" within a year!
A 3 foot tank by 2foot by 2 foot would be nice, and wouldt be the least I'd recommend.

i wasn't trying to say that oscar grow very slow, just wanted to know how long they can fit in to that tank so that i know i still have a bit of time to get a bigger tank. so you recommend a 3ft by 2ft by 2ft?

i have my oscar in a 55 by itself, the tank measures 13" across x 48" long, and the fish is 11" long. he can hardly turn around. even a 55 is not big enough IMO. i would get one of those 70 gallon ones that are wider. same length and height as teh 55 but with more room for the fish to turn around. if the fish i have in there were maxed out, it wouldnt be able to turn around.

The size I suggested will be around 90 Gl.
There's a difference between surviving a tank or thriving and being happy.
I run a 180Gl, my O is not full grown, but when he goes crazy, I think my tank is hardly big enough!lol