If you can not cope with the problem yourself, ask someone to help you. Another person is much easier to perform the action, and he is likely to be more objective. If you want to get the result of high precision - been measured several times - one on their own, the other - with the help of others. So you can not doubt the correctness of the data.
If you're going to go to the hairdresser and measure the length of hair in order to calculate in advance the cost of services wizard, you do not necessarily seek to obtain accurate data. Enough to know which of the three categories include your hairstyle: short hair, medium length hair or long hair. Considered short hair, reaching the ear lobe. If they go down a little lower, but not much in favor of the line of the shoulders, their length - the average. Followed by long or super-long hair. But the latter are rare - not everyone will be able to cope with hair coming down to the waist.
Whatever the results of the measurements do not worry. If you want to have a long, luxurious hair, you'll be sure to have them. Take your vitamins, watch your diet, carefully select shampoos and conditioners for hair. Remember that the person who strives to achieve the objectives and do not affraid of difficulties, certainly gets its way.