I dont have a link handy, but google (or bing...) 'priming calculator'. I use Rooftop Brew's, but they're all similar. They'll give an accurate amount based on how carbed you want it.
You have to input the brew temp of the beer in the tastybrew calculator as well. It makes a difference with final co2 volume,taking into account the amount of dissolved co2 after fermentation is done.
Personally I have decided against using DME in the future. Simply because the attenuation of DME is around 70%. Leaving behind added flavors/sweetness. I brewed a kick butt Weissen Doppelbock, prime with DME and now it's too sweet. ugh. 5 months and waiting...
I will switch back to table sugar if/when I bottle again.