i have a sprain anklle when will i be able to run ?

this is going to depend on the severity of the sprain and how much rest you give it. You probably should see an orthopedic doctor and get a thorough examination as they will be able to tell you when you will be able to run. Without an examination no one can give you an accurate answer.

In 1997, I sprained my ankle one morning running to get the train and was out of work for two days.

You should take it easy for a few days at least.

If you are a runner, you shouldn't try to run on it until it feels a lot better because you don't want to end up with a reoccurring injury.

Please check out this site below:

http://www.revolutionhealth.com/conditions/first-a...

If you use a bag of frozen vegetables on it, along with some pain reliever like Aleve (Naproxen if you don't have high blood pressure) and keeping that ankle elevated, it could get better in as soon as a few days if your injury was minor.