Learning to make a seat cushions pertaining to Patio Furniture

I like to watch the do-it-yourself home improvement shows and had so many ideas  to choose. One that caught my interest is  learning  to make a seat cushions pertaining to patio furniture since we have an outdoor  furniture  and I want to add a  a cushion seating. 

Measurement:

I'm not a good in measuring and I'm scared to take any risk before I order  the patio cushion seating so hubby will be the one to taking care of it and I'll be the one to sew.

Choose the material:

Choosing the material is so easy since I like the cushions that are foam only.Other than that I have to choose the fabric.

I can't wait this project to be done and share it with you.