Does anyone know how the calculation is done for hair strand tests for alcohol. I have done a lot of reading on it but can't seem to find an answer to this. I know that 1.5 inches is usually taken and that represents around 90 days. Also know that the 'cut off' seems to be around 60g of alcohol a day. Do they add up the total number of grams of alcohol consumed and divide by 90 thus giving a daily amount? Help!