How Can You Tell What Gender A Fire Bellied Toad Is?

Males generally have rougher backs and their forearms are thicker than the females... but they're almost identical... Except during  breeding season, when males get black horny  pads on their fingers and forearms... Another way to try and tell is to observe their behavior... When a toad tries to jump on the back of another toad and use the arms to grasp it, it's almost always a male.  
It's not that easy to get fire-bellied toads to breed, so I wouldn't worry about separating them even if they are male and female... If they do happen to breed you can just remove the eggs once they're laid.... If they don't eat them before get the chance. ; )
 

Usally you can tell by there webbed feet females have webbed feet only half way the male has it pretty much all the way up

The female will have long middle fingers. The male toad will have short middle fingers

If it is a boy its throat is dark but if it is a girl its throat is the same color as the belly

The male ones are suppose to bark like a puppy.

My Male jumped on our new female within two minutes of being together...

The male barks more than the female and the male has rougher skin but sometimes the alpha female does the same as a male

When it makes any noise the most that is the male.If you have a boy and a girl fire belly toad when they mate it almost looks like one is hugging the other.

Because the males are generally smaller and Males generally have rougher backs and their forearms are thicker than the females... But they're almost identical... Except during  breeding season, when males get black horny  pads on their fingers and forearms... Another way to try and tell is to observe their behavior... When a toad tries to jump on the back of another toad and use the arms to grasp it, it's almost always a male.   
It's not that easy to get fire-bellied toads to breed, so I wouldn't worry about separating them even if they are male and female... If they do happen to breed you can just remove the eggs once they're laid.... If they don't eat them before get the chance. ; )

The male has BIG arms and female has tiny arms. But it's hard to tell!!!

The male has suction pads on thier fingertips and are usually smaller than females, males have thicker arms, and smaller bumps on thier backs