Doctors say that we actually have two ages. Our calendar age, and our real age. Your real age takes into account your current health standings combined with your family history to form a better perspective of how old you really are. There are plenty of online questionnaires that can help you determine the age of your body. Of course seeing a doctor and getting the results from real testing would be most beneficial, if you're looking for a general idea of where you stand, taking time out for one of these is a good plan. Below are links to my two favorite real age tests.
Real Age is a website dedicated to the results of this test. Their daily health tips always come with a keynote of how many years each specific change in your lifestyle can take off your life. Their test has been featured on many prominent news programs and has been formulated with the help of doctors. It does take a bit of time to fill out, and has quite a few questions. If you have free time, I would suggest filing it out in spurts while completing another project. It also requires that you know about your family's medical history and your own medical history fairly in depth, although there are always options to skip questions if you are unsure.
Real Age Test Link
This next link is one for those who may not have as much time, or may not know their family history or their own medical history with detail. It allows you to move a dial on a scale to the general area you think you may stand for each question. It goes much faster than the other link, at about 34 questions in total. However, I could not find any research that linked this site to any doctor or personal with medical knowledge.
Life Expectancy Calculator
After taking both, I personally prefer the Real Age test. I think it's a bit more accurate and asks deeper questions. Even though I didn't know the answers to all of them, they were thought provoking and opened my eyes to what key issues effect health. Checking your real age is a good way to look at where you are with your health choices.