How to compare unit prices and find the better deal
Compare package sizes correctly by calculating the cost per ounce, pound, item, or other common unit.
The unit-price formula
Package price alone does not tell you which option is cheaper because packages can contain different amounts. Unit price puts both products on the same scale.
Choose one shared unit before comparing. If one label uses pounds and another uses ounces, convert them first. One pound equals 16 ounces.
Example: two different package sizes
A 16-ounce package costs $5.20, so its unit price is $0.325 per ounce. A 24-ounce package costs $6.96, which equals $0.29 per ounce. The larger package costs more at checkout but is cheaper for each ounce.
To estimate the savings, subtract the two unit prices and multiply by the amount you expect to buy or use.
When the lowest unit price is not the best purchase
The cheapest price per unit saves money only if you use the product. A larger package can be wasteful if food spoils, storage is limited, or you are trying a product for the first time.
Quality also matters. Compare like with like—similar ingredients, durability, concentration, or performance. A concentrated cleaner may appear expensive per ounce but require much less for each use.
- Check whether the units are identical.
- Account for coupons and discounts before dividing.
- Consider spoilage, storage, and how quickly you use the item.
- Compare cost per use when products have different concentrations.
How to include a discount
Calculate the sale price first, then divide by the package quantity. For a $10 item discounted by 20%, the sale price is $8. If it contains 32 units, the discounted unit price is $0.25 per unit.
Frequently asked questions
Is a lower unit price always better?
It is cheaper per unit, but not necessarily the better purchase if you will waste part of the larger package.
How do I compare pounds with ounces?
Convert pounds to ounces by multiplying by 16, then calculate both prices per ounce.
Should I include sales tax?
Usually both items have the same tax treatment, so pretax unit prices are enough. Include tax if the products are taxed differently.
Want help with the calculation?
Use the discount calculator →Published August 3, 2026 · Reviewed for clarity and source accuracy.