The B786 is a cross-country B-road in central Renfrewshire.
It starts at traffic lights on the A760 on the southern edge of Lochwinnoch. It heads north and immediately crosses a narrow bridge over the River Calder; the traffic lights at the junction also control traffic flow over the bridge. The road then continues along Main Street and High Street through the centre of town before climbing Johnshill into open country.
The B786 continues on into the hills. Although there are never any particularly steep gradients the road does divert occasionally to make sure this remains so. After a mile or so which is relatively flat the road bends to the right and starts its descent, which seems steeper than the climb. The road undulates to cross a few tributaries of the River Gryfe and crosses the B788 before reaching the river itself. On the far side of the river the road enters Kilmacolm. It heads northeast along Lochwinnoch Road and crosses a bridge over a dismantled railway line adjacent to the old station. The road continues through the town centre before ending at a T-junction on the A761.