Here's How Much You Need to Exercise If You Sit at a Desk All Day, According to Science

Readable article here:
http://www.popsugar.com/fitness/Exercise-Formula-Counteract-Sitting-42113170
Key paragraph here:
A new study, published in The Lancet, shows the ideal formula for counteracting the negative effects of a sedentary job. Instead of a fixed number of hours spent exercising, the ratio depends on how much you sit: people who work a typical eight-hour day should spend at least one hour each day moving; if you sit six hours a day, you should spend half an hour exercising. The research also indicated that the exercise doesn't have to be all at once — or rigorous. It can be spread throughout the day and be as simple as walking.
Good, because with my getting in 10,000 steps a day over 2+ hours I might ameliorate my desk job.

The research backing it up here:

Does physical activity attenuate, or even eliminate, the detrimental association of sitting time with mortality? A harmonised meta-analysis of data from more than 1 million men and women