I need a 4.5 unfinished to be 4 in finished pinwheel, any suggestions on how to acheive it??

I'm not a math person. I start with what I think will work and do a sample block, then adjust until I get what I want. Others will have a more math approach to getting the correct size. What ever works for you:)

(4) 2 7/8" squares--(2) one color--(2) background
place- draw diagonal line on light squares- place 2 right sides together- stitch 1/4" on either side of line- cut on line- press toward darker triangle.
trim to 2 1/2" squares.
lay out (4) 1/2 square triangles in a pinwheel design- stitch top two squares together- then bottom two- press alternating directions or open to reduce bulk..

Do want to do rotary cutting or foundation piecing...I just checked my EQ7 and it gives both ways...for rotary cutting you need 2 7/8 inch squares...let me know if this helps...

Rotary cut I will be able to try this out after dinner ! Thanks to everyone.