Subtract the amount completed from the total amount needed to be done to find the amount remaining. For example, if you want to raise $250 and you've raised $100, subtract $100 from $250 to find you need $150 more.
Divide the amount remaining by the total amount. In this example, divide $150 by $250 to get 0.6.
Multiply the result by 100 to find the remaining percentage. In this example, multiply 0.6 by 100 to find the percentage remaining equals 60 percent.