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Unit Price Comparison Calculator

What this does

Compare two package sizes by true price per unit and see instantly which product is the better deal.

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Runs in your browser

Calculator inputs

How to use it

Using the unit price comparison calculator

  1. 01

    Enter product A

    Shelf price and net contents, using the unit printed on the package (oz, g, sheets, loads…).

  2. 02

    Enter product B

    Same fields for the rival size or brand; keep units consistent for a valid comparison.

  3. 03

    Read the verdict

    The best-value row names the winner and quantifies the gap as a percentage.

Good to know

Bulk is usually cheaper; until it isn’t

Packaging economics favor big boxes, so per-unit prices fall with size most of the time. But promotions invert the rule constantly: a couponed small size regularly beats an uncouponed bulk one. Always run the numbers.

Mind the shrink ray

Manufacturers quietly cut contents while holding price; 16 oz jars becoming 14.5 oz overnight. Comparing today’s unit prices against what you paid last quarter exposes shrinkflation instantly.

The spoilage asterisk

Per-unit savings evaporate if the extra quantity spoils. Bulk wins only for goods you reliably finish before expiry; otherwise the cheaper sticker is the more expensive purchase.

How it's calculated

The math behind this calculator

Unit price = price ÷ package size Cheaper by % = (higher − lower) ÷ higher × 100

Each product’s price divided by its contents yields the honest per-unit cost that shelf tags obscure. We compare the two unit prices directly and report how much cheaper the winner is relative to the loser, expressed as a percentage of the worse deal.

Assumptions & limitations

  • Both sizes contain comparable goods (same brand tier or interchangeable substitute).
  • Units match; convert grams↔ounces first if they differ.
  • Prices exclude coupons and loyalty discounts unless you fold them in.

Worked example

A $4.99 12 oz jar costs about 41.6¢ per ounce while a $6.49 16 oz jar runs about 40.6¢; Product B wins by roughly 2.45% despite costing $1.50 more at the shelf.

FAQ

Frequently asked questions

Are store shelf tags reliable?
Mostly; many jurisdictions mandate unit pricing; but formats differ (some show per-pound, some per-piece). Computing your own keeps comparisons apples-to-apples.
What if the units differ, like oz versus grams?
Convert first: 1 oz ≈ 28.35 g. Our converter tools handle it, then bring both values back here in the same unit.
Does this work beyond groceries?
Anything sold in quantities: paper towels, paint, subscription plans priced per seat, even gasoline across stations.

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