If you have a coupon, subtract the coupon value from the total price before you calculate the unit price.

Some products will be sold by item, such as toilet paper, paper towels, or pencils. However, most items will have a unit of measurement, like ounces, cups, quarts, gallons, milliliters, liters, etc.

For example, let’s say you’re looking at a quart of milk for $1. 25 and a gallon of milk for $4. 29. There are 4 quarts in a gallon, so you could adjust the price for the quart of milk by multiplying it by 4. To purchase a gallon of milk in individual quart-size bottles, you’d pay $1. 25 x 4, which is $5. 00. Similarly, let’s say you’re looking at a liter of vegetable oil for $9. 79 and a 12 oz bottle for $4. 99. One liter contains 33. 8 ounces, so you can use that number as your quantity.

Let’s say the product is a 6-roll pack of toilet paper for $4. 59. To get the unit price, you’d divide $4. 59 by 6 to get $0. 77. The unit price is $0. 77. Similarly, you might be considering a 24 oz bottle of shampoo for $13. 79. Divide $13. 79 by 24, which is $0. 57.

As an example, when you’re looking at an 8 oz bottle of olive oil that costs $5. 79, you might see a unit price of $0. 72 printed in small type in the corner of the label.

For instance, let’s say you’re trying to choose between a 6-roll pack of toilet paper for $4. 59 and a 9-roll pack of toilet paper for $7. 29. To get the unit prices, calculate $4. 59/6 = $0. 77 and $7. 29/9 = $0. 81. Alternatively, you might be trying to choose between a 32-oz family-sized box of cereal for $4. 89 and a 12-oz regular-sized box of cereal for $2. 29. You’d calculate $4. 89/32 = $0. 15 and $2. 29/12 = $0. 19.

As an example, if a 6-roll pack of toilet paper has a unit price of $0. 77 and the 9-roll pack has a unit price of $0. 81, the 6-roll pack is the best choice. Alternatively, a family-sized box of cereal is a better deal at a unit price of $0. 15 versus a smaller box at a unit price of $0. 19.

For example, a toilet paper that has a thicker ply or more sheets may have a higher unit cost than single-ply toilet paper with a low sheet count. In this case, you might decide that the higher-quality toilet paper is a better value for you.