brake pad wear

I was looking at my brake calipers today.. and I was trying to understand how they work. The rotor goes in the caliper between the brake pads. Piston goes inward and clamps the pads together to stop. I was looking at the pads, the amout of brake pad material sitting pass the caliper itself between the rotor is just about 1mm, not even 1.5mm I dont think. So this means the brake pads are worn down too much and need replacing after 1mm. Is this normal ? These brake calipers I bought are supposely have brand new brake pads in them.

yeah that sounds pretty thin .post picture of pads if you can. goodluck,happy wrenching!