The sticker price is almost never the real price. A jar that costs $4.99 and a jar that costs $6.49 — which one is actually the better deal? The answer depends entirely on how much stuff is inside each jar, and shoppers who only look at the front-of-pack number overpay every single trip. This price comparison calculator turns two shelf prices and two package sizes into unit prices — the cost per ounce, per pound, per milliliter, or per count — so you can see exactly which brand is cheaper, by how much, and in what percentage.
Type in the price and size for package A and package B, and the result card instantly shows each unit price, which brand wins, the dollar gap per unit, and the percentage you would save by buying the cheaper one. No more squinting at tiny shelf tags and trying to do long division in the cereal aisle.
How to Use
- Enter the full shelf Price — Brand A. Use the price before coupons, loyalty discounts, or card-member savings; those vary by trip and distort the comparison.
- Type the Package Size — Brand A exactly as it is printed on the label — for example, 50 ounces, 1.5 pounds, 12 count, or 750 milliliters.
- Do the same for Price — Brand B and Package Size — Brand B. The two packages must use the same unit, or the comparison is meaningless.
- Pick the Unit of Measure that matches both labels — ounces, pounds, fluid ounces, milliliters, liters, count, grams, or kilograms. If one jar is sold in ounces and the other in milliliters, convert one first (1 fluid ounce ≈ 29.57 mL).
- Read the result card: Unit Price — Brand A and Unit Price — Brand B tell you the cost per single unit; Best Value names the cheaper brand; Price Gap per Unit shows the dollar difference; Savings expresses that gap as a percentage of the more expensive unit price.
The engine computes unitPrice = packagePrice / packageSize for each brand, then divides the gap by the higher unit price to express the saving as a clean percentage. A 19% saving on a staple like cereal, laundry detergent, or coffee compounds into real money over a year.
The Unit Price Formula
Unit pricing is the most useful arithmetic in the grocery store, and it is also the simplest:
unit price = package price ÷ package size
For example, if a 50-ounce box costs $4.99, the unit price is $4.99 ÷ 50 = $0.0998 per ounce. An 80-ounce box that costs $6.49 works out to $6.49 ÷ 80 = $0.0811 per ounce. Even though the second box costs more at the register, it costs about 19% less per ounce. That is the whole trick of unit pricing: the bigger package is usually cheaper per unit, but not always, and the only way to know for sure is to do the division.
The savings percentage is calculated against the more expensive unit price: ($0.0998 − $0.0811) ÷ $0.0998 ≈ 18.7%, which rounds to about 19%. If the two unit prices are identical, the calculator reports zero savings and declares a tie.
Why Bigger Is Not Always Better
Shoppers assume the largest size is always the best value, but that assumption is wrong often enough to cost you money. Manufacturers deliberately engineer "value sizes" that look like a deal but are priced at the same or higher unit rate than the regular size. Sometimes a sale on the small size beats the everyday price on the family size. Sometimes a store brand in an odd-ounce package undercuts the national brand per unit even though the national brand has a big-sale sign.
Always compare unit prices rather than package prices. The shelf tag in most US grocery stores already prints a unit price, but the unit often switches between brands (one per ounce, the next per pound), which makes direct comparison a mental conversion puzzle. This calculator removes that puzzle by forcing both sides onto the same unit and surfacing the winner in one line.
Examples
Example 1 — Cereal shelf (the worked example). Brand A is a $4.99 box of 50 oz; Brand B is a $6.49 box of 80 oz. Unit price A is $0.0998/oz, unit price B is $0.0811/oz. Brand B wins by about $0.0187 per ounce, or 18.7%. Over a year of buying one 80 oz box every two weeks (26 boxes, 2,080 oz), choosing B instead of A saves roughly $39 — on cereal alone.
Example 2 — The sale trap. A national-brand detergent is on sale for $8.99 for 64 fl oz (unit price $0.1405/oz). The store-brand equivalent is $7.29 for 48 fl oz (unit price $0.1519/oz). Even though the store brand is cheaper at the register, the national brand on sale is actually about 7.5% cheaper per ounce. The calculator makes this flip visible instantly.
Example 3 — Toilet paper bulk pack. A family-size pack has 12 rolls for $14.99 (each roll = 150 sheets, total 1,800 sheets) and a standard 6-pack costs $7.99 (each roll = 150 sheets, total 900 sheets). Unit price: bulk = $0.00833/sheet, standard = $0.00888/sheet — the bulk pack is about 6.2% cheaper per sheet. Over a year of buying one pack per month, the savings add up to roughly $6–$8, which is why checking unit price even on small staples matters.
Example 4 — Equal prices, different sizes. Two jars both cost $3.99, but one holds 24 oz and the other holds 30 oz. Unit prices are $0.166/oz and $0.133/oz — the larger jar is roughly 20% cheaper per ounce even though the shelf price is identical.
FAQ
How do I calculate the price per unit?
Divide the package price by the package size. For a $4.99 box that contains 50 ounces, the unit price is $4.99 ÷ 50 = $0.0998 per ounce. Do the same division for the competing package and compare the two per-unit numbers — the lower one is the better deal, regardless of which package costs more overall.
Is the bigger package always cheaper?
No. While larger sizes usually have a lower unit price, that is not guaranteed. Brands raise the unit price on "family size" packaging, sales on regular sizes can beat everyday bulk pricing, and store-brand odd sizes can beat national-brand large sizes. Always compare unit prices with a calculator rather than assuming bigger equals cheaper.
What does the savings percentage mean?
The savings percentage is the gap between the two unit prices divided by the higher unit price. If Brand A costs $0.0998/oz and Brand B costs $0.0811/oz, the gap is $0.0187/oz; $0.0187 ÷ $0.0998 ≈ 18.7%. That means buying Brand B instead of Brand A costs about 19% less for the same amount of product.
Can I compare packages in different units?
Not directly. You must convert both sizes to the same unit first. Common conversions: 1 pound = 16 ounces, 1 fluid ounce ≈ 29.57 milliliters, 1 liter = 1,000 milliliters, 1 kilogram = 1,000 grams. Once both packages are measured in the same unit, enter them here and the comparison is valid.
Should I use the price before or after coupons?
Use the shelf price for a fair side-by-side comparison. Coupons, loyalty discounts, and card-member pricing differ between brands, shoppers, and trips; if you apply a coupon only to one brand, recalculate that brand's net price first. For everyday stock-up decisions, the everyday shelf price is the more stable number.
What if the two unit prices are equal?
The calculator reports a zero-percent saving and declares a tie. In that case choose whichever package size fits your pantry, fridge, or budget; prefer the smaller one if the product expires quickly, and the larger one if it is a non-perishable staple.
Does this work for non-food items?
Yes. Unit pricing applies to anything sold by weight, volume, or count: laundry detergent, paper towels, pet food, coffee, batteries by the count, bottled water, and skincare products. The math is identical — divide the price by the printed net contents.
Related Calculators
- Unit Price Calculator — single-product unit price when you only have one package to evaluate.
- Coupon Calculator — apply a coupon or loyalty discount to the net price before comparing two brands.
- Sales Tax Calculator — add state and local sales tax so the out-the-door prices match what the register rings up.
- Bogo Calculator — figure out which "buy one, get one" promotion really wins per unit.
- Profit Per Unit Calculator — flip the math around to see your own margin on each item sold.
Disclaimer
This price comparison calculator is provided for informational purposes only and does not constitute financial, shopping, or purchasing advice. Unit prices are computed from the inputs you enter and are approximations based on the package sizes you provide; actual shelf prices, net contents, coupons, and discounts vary by store and by day. Always confirm the net weight or volume on the label and the final checkout price before buying. Neither Smekys nor the calculator's authors are responsible for purchasing decisions made based on these estimates.