The only way in which you are going to successfully find the DRI for protein that you need if by going a calculator online. For a 180 lbs male, it is suggested that you have around 66g of protein on a daily basis, however you will need to confirm this with your doctor as each as everyone of us is different and may need more than the guidelines which are in place, or even less. A male which is 40 may need ore DRI of protein than a young male, but this is also going to need to be calculated due to the body type that you have and how your body works.
There are not two people who are exactly the same and therefore you are going to have to ensure that you go to the doctors so you are going to be getting the right amount for you and no one else. If you do not want to do this, there are guidelines in place such as the 66g, but these are only guidelines and are not going to apply to everyone as we are all different. To be sure about how much DRI of protein you should be getting a day, you can always go to different dieticians and doctors which can run test to ensure that you are going to have the right amount for you.
Alternatively, if you do not want to do this, you can always try to get as close to the guidelines as you can when it comes to the amount of protein you are going to have on a daily basis. If you can get as close as possible you are at least ensuring that you are going to be as healthy as you can and give your body everything that it is going to need on a basic level.
There are not two people who are exactly the same and therefore you are going to have to ensure that you go to the doctors so you are going to be getting the right amount for you and no one else. If you do not want to do this, there are guidelines in place such as the 66g, but these are only guidelines and are not going to apply to everyone as we are all different. To be sure about how much DRI of protein you should be getting a day, you can always go to different dieticians and doctors which can run test to ensure that you are going to have the right amount for you.
Alternatively, if you do not want to do this, you can always try to get as close to the guidelines as you can when it comes to the amount of protein you are going to have on a daily basis. If you can get as close as possible you are at least ensuring that you are going to be as healthy as you can and give your body everything that it is going to need on a basic level.