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Divide the total cost of each product by the quantity in the package. Get the unit price for each item. 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. Generally, the product with the lowest unit cost is the best value. Compare the unit prices that you calculated to see which one is lower. Then, purchase that product. 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. Typically, items that are of lesser quality will have a lower unit cost. You might still choose to purchase the less expensive item. However, consider the quality of the items when making a final purchasing decision. 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.

Summary:
Calculate the unit price of the items you're planning to buy. Choose the item with the lowest unit price. Make sure that the quality of the items is similar, if that matters to you.