Calculate Unit Price Calculator
Big bag vs small box? Enter both prices and sizes — we'll convert the units and tell you which one is actually cheaper.
Product A
Product B
| Product A unit price | — |
| Product B unit price | — |
| Savings vs the other | — |
How it works
Unit price = price ÷ quantity, converted to a common base unit. Weights convert to ounces (1 lb = 16 oz, 1 kg ≈ 35.27 oz), volumes to fluid ounces (1 gal = 128 fl oz, 1 L ≈ 33.81 fl oz), and counts compare per item. Products must be in the same category (weight, volume, or count) to compare.
Formula & worked example
Formula: Unit price = price ÷ quantity, after both products are converted to a common base — ounces for weight, fluid ounces for volume, items for a count. The lower unit price wins, and the saving is the difference ÷ the higher unit price × 100.
Worked example: Product A at $4.50 for 12 oz costs $0.3750 per oz; product B at $7.00 for 20 oz costs $0.3500 per oz. B wins — 6.7% cheaper per ounce.
When to use this
- Two pack sizes of the same product sit side by side and the bigger one is not obviously the better buy.
- One product is priced by weight and its rival by volume or count, and the shelf tags do not use matching units.
- A favourite product quietly shrank and you want to prove what the new pack really costs per ounce.
- You are stocking a pantry or a small business and buying the cheaper unit price in quantity over a year.
How to use it, step by step
- Enter product A's price and quantity, and choose its unit — weight, volume or count.
- Enter product B the same way; the units can differ (grams against kilograms, ounces against pounds) as long as both are the same kind of measure.
- Click Compare deals and read each product's price per base unit — ounces for weight, fluid ounces for volume, per item for counts.
- Check the savings line: it states how much cheaper per unit the winner is, as a percentage of the loser's unit price.
- If the kinds of measure differ — a weight against a volume — the tool will say it cannot compare, because there is no honest conversion without knowing the product's density.
What the inputs mean
| Input | What it is | Typical values |
|---|---|---|
| Price (A and B) | The shelf price of each product | Full pack price, including any sale price in force |
| Quantity (A and B) | How much product the price buys | Read it off the pack: net weight, volume or count |
| Unit (A and B) | The measure the quantity is stated in | Weight: oz, lb, g, kg. Volume: fl oz, ml, L, gal. Or a plain count |
Another worked example
Two bags of ground coffee: product A is $6.49 for 500 g and product B is $10.99 for 1 kg. Converted to ounces, A works out to $0.3680 per oz and B to $0.3116 per oz, so product B wins — 15.3% cheaper per ounce — even though its bag costs $4.50 more at the shelf. On a household that buys coffee every fortnight, that unit gap is the difference worth stocking up on.
Frequently asked questions
What is unit price?
The cost of one unit — one ounce, one liter, one item. Grocery shelves show it on price tags; this calculator does the same math when the units don't match.
What is shrinkflation?
When the package gets smaller but the price stays the same. Unit price exposes it instantly: the "same" $5.99 bag at 14 oz instead of 16 oz costs 15% more per ounce.
Is store brand always cheaper?
Often but not always — sale prices on name brands can beat store brands per unit. Run both through the calculator during the sale and stock up when the unit price is lowest.
Why does the bigger pack sometimes lose?
Pack size and price are set independently, and retailers know shoppers assume bulk is cheaper. Promotions on the small pack, warehouse pricing on one size only, or a quiet price rise on the family pack can all flip the ranking — which is why the unit price, not the pack size, is the number to trust.
Shelf tags here show a price per 100 g — how does that relate?
It is the same idea on a different base: price per 100 g is just the unit price scaled up so the numbers are readable. This calculator reports weight per ounce, so the figures will not match the tag digit for digit, but the ranking of two products will be identical on either base.
Can I compare a product sold by weight with one sold by volume?
Not honestly, and this tool refuses rather than guess: converting grams to millilitres needs the product's density, which differs for flour, oil, honey and everything else. Compare weight with weight and volume with volume, or weigh the volume product yourself if the comparison really matters.
🏷️ Stretch every dollar
Pair this with our discount calculator for sale prices.