Unit Price Calculator

Package A price:

Enter the full price for the first package or multipack.

Package A size:

Use the quantity from one package, such as 16 oz, 500 g, 1.5 L, or 24 count.

Package A pack count:

Multiplies the printed package size when the price covers a multipack.

packs

Package B price:

Enter the full price for the competing package or bundle.

Package B size:

Use a size from the same measurement family as Package A for a direct comparison.

Package B pack count:

Multiplies the printed package size for a bundle or case.

packs

Compare as:

Pick the shelf-label unit you want displayed in tables, charts, and exports.

Package A label:

Optional short label for receipts, quotes, or shelf tags.

Package B label:

Optional short label for the comparison package.

Shared discount:

Use only for the same coupon or sale rate across both packages.

Shared checkout fee:

Leave 0 for in-store shelf tags or when fees are not comparable.

Usable amount:

Keep 100% unless some of the package will not be usable before it expires or is prepared.

Currency symbol:

Use a short symbol such as $, EUR, GBP, RM, or SGD.

Unit price decimals:

Use 2 for normal price labels or 4 for small per-gram and per-ml comparisons.

decimals

Package	Effective price	Normalized size	Unit price	What it tells you	Copy
{{ row.package }}	{{ row.effectivePrice }}	{{ row.normalizedSize }}	{{ row.unitPrice }}	{{ row.note }}

Signal	Action	Reason	Copy
{{ row.signal }}	{{ row.action }}	{{ row.reason }}

Scenario	Size	Shelf price	Limit price	Note	Copy
{{ row.scenario }}	{{ row.size }}	{{ row.shelfPrice }}	{{ row.limitPrice }}	{{ row.note }}

Enter compatible package sizes to render the unit price ladder.

Enter compatible package sizes to render the shelf price limit chart.

{{ jsonPretty }}

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Unit price turns unlike package labels into a common value question. A larger bag, bottle, bundle, or case is a better buy only when its price per comparable unit is lower and the extra quantity will actually be used.

Two packages normalized to the same unit price basis

Good unit-price comparison needs matching measurement families. Weight can compare with weight, volume with volume, and count with count. A price per ounce cannot be compared directly with a price per milliliter unless the product density or conversion is known.

The cheapest normalized unit price is not always the best purchase. Freshness, brand, storage space, spoilage, and the amount you need can outweigh a small savings gap.

Technical Details:

Unit price divides an effective package price by a normalized quantity. The effective price can include a shared percent discount and a shared checkout fee. The normalized quantity multiplies the printed package amount by pack count, converts it to a base unit, and applies the usable-amount percent.

The comparison target then expresses both packages as price per count, per 100 g, per kg, per ounce, per liter, per gallon, or another compatible label. The same target must be used for both packages before a lower value means a lower unit price.

unit price = \frac{effective price}{normalized usable quantity} \times comparison unit size

Unit price calculator mechanism fields
Field	How it affects the result	Boundary
Package price	Starting shelf, quote, or checkout price.	Values below zero are treated as zero.
Package size	Printed quantity before unit conversion.	Must be positive to calculate a package row.
Pack count	Multiplies the printed size for bundles or cases.	Rounded to at least 1 pack.
Shared discount	Reduces both package prices by the same percent.	Clamped from 0 to 100 percent.
Shared checkout fee	Adds the same delivered-price fee to each package.	Negative fees are treated as zero.
Usable amount	Models waste, trimming, spoilage, or unusable quantity.	Clamped from 1 to 100 percent.

Break-even shelf price reverses the calculation: it asks what another package size could cost while matching the best current base-unit rate after the same discount, fee, and usable-amount assumptions.

Everyday Use & Decision Guide:

Start with the exact shelf prices and the printed sizes for Package A and Package B. Leave Compare as on Match Package A shelf unit unless you need a specific shelf-label basis such as per 100 g, per ounce, or per count.

Use advanced inputs only when they describe both options fairly. A shared coupon belongs in Shared discount. Shipping or delivery that applies to each option belongs in Shared checkout fee. Spoilage, trimming, or waste belongs in Usable amount.

If the summary says Unit mismatch, convert the package labels before comparing.
If the Spread badge is small, quality or freshness may matter more than the arithmetic savings.
If the best unit price costs more at checkout, check whether the larger purchase fits your budget and storage.
Use Equivalent Price to decide the maximum shelf price a different package size should have.

The result is strongest for like-for-like goods. It should not decide between different formulas, brands, ingredients, warranties, or quality grades without human judgment.

Step-by-Step Guide:

Build the comparison from package facts, then read the normalized result.

Enter Package A price, Package A size, and Package A pack count. The package needs a positive price and size to appear as a valid row.
Enter Package B price, Package B size, and Package B pack count. Use the same measurement family as Package A.
Choose Compare as. If a selected target does not match Package A's unit family, the calculator falls back to a compatible target.
Add Shared discount, Shared checkout fee, or Usable amount only when those assumptions apply to both packages.
Read Unit Price Ledger for effective price, normalized size, and unit price. If a row says Not comparable, fix the unit family before trusting the comparison.
Use Unit Price Guidance and Break-Even Shelf Price to judge whether the spread is material and what other package prices would need to be.

When the summary identifies a lower unit price, verify the displayed unit before using the result in a cart or quote comparison.

Interpreting Results:

Unit Price Ledger is the main audit table. It shows each package's effective price, normalized size, unit price, and comparison note. The lower unit price wins only among valid, compatible rows.

A Spread below the material threshold shown in Unit Price Guidance can be too small to outweigh brand, freshness, or convenience. A large spread is more useful, but it still assumes the same usable percent and measurement basis.

Do not read Break-Even Shelf Price as a forecast or sale price. It is a limit: a package at that size must be at or below the shown amount to match the current best rate.

Worked Examples:

Package A costs 4.79 for 16 oz, and Package B costs 7.99 for 28 oz. With Compare as matching Package A, Package A is about 0.2994 per oz and Package B is about 0.2854 per oz. The summary names Package B as the lower unit price and shows a spread of about 4.7 percent below Package A.

A 500 g bag at 6.00 and a 750 g bag at 8.50 compare at 1.20 per 100 g and about 1.13 per 100 g. If Usable amount is changed to 80 percent for both, the unit prices rise because only part of each bag is counted, but the larger bag still wins under the same waste assumption.

A 16 oz jar cannot be compared directly with a 500 ml bottle in this tool. Unit Price Ledger marks the incompatible row because weight and volume need product-specific density before they can share a unit basis.

FAQ:

Can I compare ounces with grams?

Yes. Ounces, pounds, grams, and kilograms are all weight units, so they can be normalized to one weight target such as per oz or per 100 g.

Why does the tool reject weight versus volume?

Weight, volume, and count are different measurement families. A fluid ounce and an ounce are not interchangeable unless you know the product density and convert outside the calculator first.

Does the cheapest unit price always mean I should buy it?

No. The Unit Price Guidance rows call out small spreads, higher upfront cost, and usable-quantity assumptions because a lower unit price can still be the wrong purchase.

What does usable amount change?

Usable amount reduces the quantity counted in the denominator. Setting it to 80 percent makes the same price spread across less usable product, raising the displayed unit price.

Glossary:

Unit price: Price expressed per comparable unit, such as per oz, per 100 g, or per count.
Effective price: Shelf price after the shared discount and shared checkout fee are applied.
Normalized size: Package quantity converted to the selected comparison unit.
Break-even shelf price: The highest shelf price another package size can have while matching the best unit rate.

References:

NIST SP 1181 - Unit Pricing Guide, National Institute of Standards and Technology, December 17, 2014, updated July 14, 2025.