JR pass or individual purchase

Hi,

During my stay in Japan at some point I will travel the following routes on the bullet train:-

Tokyo to Kyoto (and back again)
Kyoto to Osaka (and back again)
Kyoto to Hiroshima (and back again)

I may also go to places just outside Tokyo.

I'm staying for two weeks in Japan but will at max need the bullet train for just a week as I'm staying in Tokyo for a week. My question is with this itinerary would it be worth it to buy a one week pass or would it be cheaper to pay individual prices when I'm there?

Thanks.