Definitely weigh it. For convenience weigh it out before hand and put in separate bags so that in the morning you just have to pick out a bag. This will help avoid the temptation to guesstimate when you're in a rush.
I was guessing to start with and my weight loss slowed down so I bought some digital scales and now im flying along much better!
I used to have Raisen wheats and never measured them, but when i decided to measure them today i could literally have 8 pieces!!
Now i use 5 syns to have honey cheerios and its well worth it
i've weight it now, only a miniscule amount isnt it!! ive got banana to top it up with. now a question... ive got kellogs bran flakes its counted as my healthy extra isnt it and i dont have to syn it do i??