Compare the price-per-unit of two products to find out which one is really the better deal.
Unit price is the cost of a single unit of a product (per ounce, per item, per liter, etc). Comparing unit prices - not just the sticker price - is the only reliable way to tell which package size is actually cheaper.
Unit Price = Total Price ÷ Quantity
A 12-pack costing $4.99 works out to $0.4158/can, while a 24-pack costing $8.99 works out to $0.3746/can - the 24-pack is the better value even though it costs more upfront.
Total price ÷ quantity, letting you compare cost per standardized unit.
Larger packages aren't always cheaper per unit.
Different natural units for different products can make direct comparison harder.