It is important to choose correct size when you´re buying mens jeans because you want them to fit you just right. If you get it wrong they will probably, not just fit badly but also be uncomfortable.
So it is important to follow these rules:
1. Make waist measurement just little above hips. Measure hip circumference also. Make sure to leave at least one finger size between waist and jeans sizes. That will make them more comfortable.
2. Wear your usual shoes and measure leg length. They should be 1 to 2 centimeters above ground.
3. You can use old jeans that fit you well as example for measurement also.