pedal is soft at the bottom

With new calipers, it is likely that the front brakes have not be properly bled to get all the air out of the lines and out of the new calipers. Did the brake fluid all run out of the master cylinder when the new calipers were installed? If so, then the rears need to be bled too.

Are you doing this work yourself? Make sure the new calipers up front are installed with the bleeders pointing up. If swapped side to side, the bleeders will point down and you will never get them properly bled.