Use the Naismith Law to estimate the time required for your hike. According to this law, a fit adult can cover 5 km of level ground per hour, and an extra hour should be added for every 600 m of uphill hiking. For hiking in Hong Kong, it is best to base on an hourly rate of 4 km for level ground, and an extra hour for every 500 m of uphill hiking. Please note that these estimated rates do not include short breaks, and have not taken into account factors like weather conditions, load and loss of energy.