Convert the percents that are to be added into fractions. Divide them by 100. For example, 50 percent would convert to 50/100. The percent is an expression of a fraction, and converting it to its original form may reduce the chance of error when adding.
Add the fractions together. When adding the fractions, the numerators (top numbers) are added together and the denominator (bottom number) stays the same. For example, if you add 25/100 (25 percent) and 20/100 (20 percent), the result would be 45/100.
Convert the fraction to a percent. Divide the numerator by the denominator using a calculator or by hand. The result is 0.45. Then multiply by 100 to obtain the result, 45 percent.