Go to www.crutchfield.com. On the side you will see a "car products" column. Click on "what fit's my car?" and put in your car type. It will tell you all factory speaker sizes as well as the size deck you need if replacing that. You can also buy the stuff there,too. They are really good people there. They stand behind their stuff and have excellent tech support.
You don't need to cut the wires at all, I just got mine installed in 5 minutes with the adapter speaker plug, I got them from Amazon for 16 bucks but you save a lot of time and you don't mess the wire system of your car with the black tape and stuff.
That depends slightly on wether or not your Civic is a 2 door or a 4 door. On 4 door Civics the rear speakers are 6.5" round speakers. If you have a coupe the rear speakers are 6x9. The front speakers, whether sedan or coupe are 6" round. The front speakers require a pretty thin setup. I believe there is only about 2 inches of clearance depth for the speakers, so you should choose accordingly.
I just had some put in and they are 6 1/4 round speakers. Make a great difference . Could not belive when I got the car no speakers in the back good luck
6.5" round speakers in the front and back.
6.5 inch round speakers
6.5" round speakers.
6 1/2 inch round. ..
i believe the rear speakers are 5x9 and the front are 51/2 round
4" round in front and 6x9 in back
front door speakers are 6.5 inch (round) with a dome tweeter seperate, and the rear speakers above the rear headrests in the corners are 4x6
Front and rear are both 6.5" round