In order to determine which is bigger, 1/8 or 3/16, there are two different techniques (both provide the same answer).
First, we could find a common denominator for both fractions. Once we have a common denominator, we can compare the numerator for 1/8 and 3/16. If the denominator is the same for both fractions, whichever has a larger numerator is the larger fraction.
Second, we could also divide 1 by 8 and get 0.125. Then we divide 3 by 16 and get approximately 0.1875. This allows us to see that 3/16 is a larger fraction than 1/8.
The benefit of using a calculator to change the fraction to a decimal (or you could do it by hand) is that it works on fractions that are similar. For example, 4/11 and 5/12.
Either way, the fraction 3/16 is greater than the fraction 1/8.