To enable metric measurements, head over to the "Me" tab of your Dashboard and click "Edit Profile" under the "My Stuff" menu on the left side of the page. Then scroll down to the heading "Account Settings."
Look for the "System of Measurement" option to the right side of the page. Then click the bubble labeled "Metric System."
Click "Save Changes" at the bottom of the page, and your account will use the metric system for all measurements.