Calculator comparison
Unit Price vs Sale Price
A sale label describes a price reduction; unit price compares the cost of the same quantity. Use both pack size and the actual discounted price.
Updated 16 October 2026 • Tools by Layna Editorial Team • General information
The discount is only one part of the comparison
Sale price = regular pack price × (1 − discount percentage ÷ 100). Unit price = actual pack price ÷ pack quantity. To compare different pack sizes, express both quantities in the same units and compare equivalent products.
The calculator above compares Option A’s entered price with Option B’s calculated sale price. Its per-unit results use the exact quantity unit you entered: dollars per gram if both quantities are grams, or dollars per item if both are item counts.
Worked example using the calculator’s starting values
| Option | Pack calculation | Cost per 100 g |
|---|---|---|
| A | $8.50 for 500 g | $8.50 ÷ 500 × 100 = $1.70 |
| B on sale | $12 × (1 − 0.20) = $9.60 for 750 g | $9.60 ÷ 750 × 100 = $1.28 |
Option B has the lower unit price even though it costs $1.10 more at the checkout. Buying 750 g at A’s rate would cost $12.75, compared with B’s $9.60, a $3.15 saving across the 750 g quantity.
The tool’s raw per-gram outputs are $0.0170 and $0.0128. Multiplying both by 100 converts them to the more readable per-100 g comparison without changing which is cheaper.
Make the quantities comparable
- Convert kilograms to grams before comparing with a gram entry; do the same for litres and millilitres.
- Do not compare grams directly with millilitres unless the relevant density is known.
- Use comparable usable quantities, such as the relevant drained weight, when that is the meaningful product basis.
- For multi-buys, enter the total payable and total quantity you actually receive.
A low unit price is useful only if the product meets the same need and you can use the quantity. If half of the larger pack is discarded, its cost per amount actually consumed doubles.
Read the saving in context
The calculator compares unit rates; it does not predict expiry, quality, storage cost or how much you need. “Saving across B quantity” compares the rates at B’s quantity and is not always an amount you can realize by buying a fraction of A’s pack.
A discount percentage compares a product with its stated reference price. It does not establish that it beats another brand, size or store. Check the current payable price and unit rate together.
Use the relevant calculator
Frequently asked questions
Is the biggest discount always the cheapest option?
No. A heavily discounted pack can still have a higher cost per equal quantity than another product.
Why does the calculator show a tiny per-unit number?
If quantity is entered in grams, the raw result is dollars per gram. Multiply both rates by 100 to compare dollars per 100 g.
Can I compare a 500 g pack with a 1 kg pack?
Yes. Enter quantities as 500 and 1,000 grams, or 0.5 and 1 kilogram. Use the same unit for both.
Sources and method
The worked figures are illustrative arithmetic. The references below explain the underlying definitions and limits.