How much time should we calculate for a visit at Jinshanling?

I think you need to spare around 5 hours at least for your visit. THe bus from Wangjingxi to the wall needs at least one hour to reach the wall. If you miss the direct bus that departs from Wangjingxi to the wall, you can take the bus from Wangjingxi to Luanping and get off at the highway rest area. It takes around 40 minutes to arrive. Then you need to wait for the free shuttle bus. So you atl east need around 3 hours on the way and spend two hours on the wall.