The longer a person is out of school, the easier it is to forget how to use percents and other basic business math formulas. Computer programs, cash registers and automated point-of-sale systems can easily complete the percentage calculations; however there will be moments when retailers will need to process the numbers manually.

There are three parts to a percentage problem: rate, base and percentage amount. The rate is the percent, the base is the total and the percentage amount is a fraction of the amount.

### Calculating Percentage Amount

To find the percentage amount, change the rate to a decimal and multiply by the base.

**Percentage Amount = Rate x Base**

Example #1:

Find 25% of $150

Percentage Amount = .25 x 150

Percentage Amount = $37.50

Example #2:

If your weekly salary is taxed 30%, how much is deducted if you make $295 a week?

Percentage Amount = .30 x 295

Percentage Amount = $88.50

### Calculating Rate

To find the rate, divide the base into the percentage amount. Because our rate is a percent, move the decimal two places to the right and add a percent sign.

**Rate = Percentage Amount ÷ Base**

Example #1:

15 is what percent of 75

Rate = 15 ÷ 75

Rate = .20

Rate = 20%

Example #2:

If you received a shipment from a vendor consisting of 250 widgets, but 65 were broken during transport, what percent are damaged?

Rate = 65 ÷ 250

Rate = .26 or 26%

### Calculating Base

To find the base, divide the rate into the percentage amount. Again, because rate is a percent, move the decimal two places to the right and add a percent sign.

**Base = Percentage Amount ÷ Rate**

Example #1:

$150 is 45% of what amount?

Base = 150 ÷ 45%

Base = $333.33

Example #2:

On Christmas Eve, your store sells a total of $2500. It was 85% of the total sales for the year. What are your store's sales?

Base = 2500 ÷ 85%

Base = $2941.17

### Calculating Percentage Increase/Decrease

To find the percent up or down, first find the difference between the two amounts. Then divide that number by the first of the two amounts. Finally, convert the fraction to a percent by moving the decimal two places to the right and adding a percent sign.

**% Increase/Decrease = Difference Between Two Figures ÷ Previous Figure**

% Increase/Decrease = (This Year - Last Year) ÷ Last Year

% Increase/Decrease = (Planned $ - Actual $) ÷ Planned $

Example #1:

If Easter sales were $5200 this year and last year they were only $3400, what was the percent increase?

% Increase = 5200 - 3400 ÷ 3400

% Increase = 52.9%

Example #2:

If your store's sales for February were planned at $22,500 and actual sales were $18,000, what was the percent reduction?

% Decrease = 22500 - 18000 ÷ 22500

% Decrease = .20 or 20%