You can easily get a fat caliper on amazon or eBay. Price range goes from €/$5 to €/$40+. I payed €6 for mine.
There are many online body fat calculators. I used the website linear-software.com but feel free to use any you wish. Simply insert your age, gender, weight and measurements to get your body fat %.
Take this measurement midway between your armpit and nipple. Don't be afraid to grab the fat. Repeat it a couple of times and use the average on the body fat calculator.
Vertically fold your skin, one inch to the right of your belly button. Again, take the measurement a couple of times and use the average.
Vertically fold your skin and take the measurement midway between you knee cap and the top of your thigh.
You are done! Don't forget to check my many other guides. Women's Guide coming soon.