Unit Price Calculator
Use this unit price calculator to find out which product is actually the better value. The bigger pack isn't always cheaper per unit. Enter the price and size of two options — in the same unit — and the calculator shows the cost per unit for each and how much you save by choosing the better one.
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Compare unit prices
Enter values above and press Calculate to see your result.
Formula used
Unit price is simply the price divided by the quantity:
Unit price = Price ÷ Quantity
Compare the two and the lower number wins. The percentage saving is the difference relative to the more expensive option:
Saving % = |A − B| ÷ larger × 100
The only rule: enter both quantities in the same unit (both grams, or both millilitres) so the comparison is fair.
Worked examples
Groceries. $3 for 500 g vs $5 for 1,000 g: A is $0.006/g, B is $0.005/g — B is ~17% cheaper per gram.
Drinks. $1.20 for 330 ml vs $2.50 for 1,000 ml: the big bottle wins per ml.
Multipacks. Compare price per item to see if the bundle truly beats singles.
How to use this calculator
- Pick the unit you'll compare in (grams, millilitres, items, etc.).
- Enter option A's price and its size in that unit.
- Enter option B's price and size.
- Press Calculate to see each unit price and the better deal.
- Make sure both sizes use the same unit — convert first if needed.
Quick unit-price tips
| Situation | What to compare |
|---|---|
| Different pack sizes | Price per gram / ml |
| Multipacks vs singles | Price per item |
| Concentrate vs ready-to-use | Price per made-up serving |
| Sale vs everyday | Unit price after discount |
Shelf labels often show unit prices — but not always in the same unit, so it pays to check.
Who should use this calculator
Anyone grocery shopping, comparing online deals, or deciding between pack sizes. It's especially handy when stores list prices per different units, or when a 'bigger is cheaper' assumption needs checking.
Why the bigger pack isn't always cheaper
Retailers know shoppers assume larger means better value, and sometimes price accordingly — or a smaller pack is on promotion. Comparing the actual cost per unit removes the guesswork and occasionally reveals that the small or medium size is the real bargain.
Comparing fairly
- Use the same unit for both — convert kg to g or L to ml first.
- Match what you'll use — for concentrates, compare per made-up serving, not per bottle.
- Factor in waste — a bulk buy is only cheaper if you actually use it before it spoils.
Limitations of this calculator
It compares price per unit only. It can't judge quality, freshness, whether you'll use a large quantity in time, or non-price factors like brand and ingredients. Use it as one input into a sensible buying decision.
Frequently asked questions
How do I calculate unit price?
Divide the price by the quantity. $3 for 500 g is $0.006 per gram. Compare two products' unit prices to see which is cheaper.
Is the bigger size always cheaper per unit?
No. Promotions and pricing tricks mean smaller packs are sometimes better value. Always compare the cost per unit.
Do both products need the same unit?
Yes. Convert so both quantities are in the same unit (e.g. both grams) before comparing, or the result will be misleading.
How do I compare multipacks?
Use 'items' as the unit and enter the number of items in each option to get the price per item.
Should I always buy the lowest unit price?
Not necessarily — consider whether you'll use it before it expires, plus quality and storage. Unit price is one factor, not the whole decision.