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It is estimated that hair grows, on average, 1 millimeter every three days, which is about 1 centimeter per month and 12 centimeters per year. The speed may vary from one individual to another, but remains constant for each one. This means that there is no point in, for example, cutting your hair on the day when the Moon changes phase. Trimming the ends to give the strand strength and speed up growth is just as pointless. Another widespread belief – and also without any scientific basis – is the one that advocates the use of diets to increase hair length. What can be affected is the rate of hair loss. It is normal to lose 100 to 150 a day.