Cut Hair Short to Make it Straight

A: No. Cutting your hair does not change its natural texture. Hair grows according to its genetically determined wave pattern - which is dictated by the shape of the hair follicles beneath the scalp - unless the follicles themselves have been altered by factors such as hormonal changes, certain health conditions, medications, or damage. Simply cutting the hair, no matter how short, cannot permanently make curly hair grow in straight.
However, the appearance of your hair can change significantly depending on its length. If you have loose waves or large curls, cutting the hair short may leave it too short to complete a full curl. As a result, the hair may appear straighter or only slightly wavy, even though the natural curl pattern has not changed. As the hair grows longer, the curls will become more noticeable again.
For individuals with tightly curled or coily hair, the curl pattern begins very close to the scalp. In these cases, cutting the hair short will not make it look straight. In fact, removing the visible curl entirely would require cutting the hair extremely close to the scalp or shaving it completely.

Hair length and weight also play a major role in the way curls look. Long curly hair is heavier, and that weight naturally pulls on the strands, stretching the curls and making the hair near the scalp appear straighter. After the hair is cut, that weight is removed, allowing the curls to spring back to their natural shape. This is why many people are surprised to find that their hair looks curlier after a haircut than it did when it was longer.
The amount of shrinkage varies from person to person. Some people notice only a slight increase in curl bounce, while others may see their hair appear significantly shorter once it dries because the curls have tightened up without the weight dragging them down.
©Hairfinder.com
See also:
Hair straightening
How to maintain curly hair
Is it true that curly hair goes away as we age?