How often should you get your hair cut? It depends on the shape

The most common advice is to get your hair cut every six to eight weeks. That is about as precise as saying everyone takes a size 8 shoe — it is true for some people.

Hair grows roughly a centimetre and a half a month. When that starts to be a problem depends on what is holding the shape together.

A short, precise shape: four to six weeks

A short bob, a pixie, and any cut that ends at the neckline or at the ear shows the growth quickly. Two centimetres is enough for the nape to fall apart and the shape to lose its line.

If you have short hair and it matters that it holds, count on four to six weeks.

A layered cut: six to ten weeks

Layers tolerate growth better, because the differences in length already give a soft transition. The problem is not the extra length so much as the layers getting heavy and the shape going flat.

If you notice that your hair no longer holds a shape after brushing, that is probably what is happening.

Long hair: eight to twelve weeks

On long hair, cutting is maintenance: taking off the broken, thinned-out ends. If you leave them, the breakage travels up the shaft, and in the end more has to come off than you wanted.

There is no point stretching it past twelve weeks, even if you are growing your hair out — growing it out is exactly when intact ends matter most.

Coloured hair: follow the colour rhythm

If you colour regularly, it is simpler to tie the two together. Root or full colour with a cut is one appointment, and the fresh colour reads as more even with the ends taken off.

If you are growing it out

Many people drop the cut entirely, and that is the most common mistake. Half a centimetre every two or three months does not slow the growth — hair grows at the root, not at the end. What it does is stop you having to take ten centimetres off later because of breakage.

A simple test

Comb your hair through and look at the ends in the light. If the tips are lighter and thinner and the hair splits at the end, it is due. That is more reliable than the calendar.