Write the first part of the term "one-quarter" that's before the hyphen as a number in the numerator of a fraction over the fraction bar. For example, write "1/" as the numerator for the portion "one" that's before the hyphen.
Write the second part of the term that's after the hyphen as a number in the denominator of the fraction to designate the number of equal parts the fraction represents. For example, "quarter" is the second part of the term after the hyphen, and a quarter represents four equal parts. So write "4" as the denominator in the fraction. This equals 1/4.
Divide the fraction's numerator by the denominator to convert the fraction to a decimal. For example, divide 1 by 4. This equals 0.25, which is one-quarter converted to a decimal.