How far can you push the pedal after the pads first push against the rotors? You should be able to feel first contact (about 1" of pedal travel)... then use a ruler and let us know how much further down you can push the pedal with your hand from that point.

If you can push it another 1"+ you probably have air in the lines, and need to bleed the brakes correctly. Air compresses, fluid doesn't.

Also check the obvious stuff if you haven't already, like even pad wear, fluid level, cap tightness.