How to use this calculator
- Enter the price of Item A and its size or quantity (grams, ounces, count and so on).
- Enter the price and size or quantity of Item B in the same unit.
- Read which item is cheaper and by what percentage, then check the price per unit and per 100 units.
- Convert units first if the packs differ, for example kilograms to grams.
How unit price works
The unit price is the price divided by the amount you get. Dividing both products the same way puts them on equal footing, so a large pack and a small pack can be compared fairly even when their sticker prices look nothing alike.
Unit price = Price ÷ Quantity- Price = what you pay for the pack
- Quantity = size or count in one consistent unit
- Saving % = (higher unit price − lower unit price) ÷ higher unit price × 100
The calculator also scales the result to 100 units, because unit prices are often tiny numbers such as $0.0099 per gram that are hard to read.
Example: 500 g versus 1 kg
A 500 g pack costs $4.99 and a 1,000 g pack costs $8.49. The small pack works out to about $1.00 per 100 g and the large one to $0.85 per 100 g.
Item B is therefore cheaper per unit by 14.93%. Buying the large pack saves money only if you will use it all; if half goes to waste, the small pack costs less in practice.
When the cheaper unit price is not the better deal
A lower unit price helps only if you will use the whole amount before it spoils or goes out of date. Food, cleaning products and anything with a shelf life can turn a bargain into a loss.
Check storage space, how fast you use the item and whether the quality is the same. Loyalty prices, coupons and multibuy offers also change the real price, so enter the final price you pay. The discount calculator shows the price after a percentage off.
Tips for shopping by unit
- Compare in the same unit; shelf labels sometimes use different ones for neighboring products.
- Watch for "shrinkflation": the same price for a smaller pack changes the unit price.
- Count real servings or sheets, not the number of packs.
- Store brands often have a lower unit price for a similar product.
- Include tax if it differs between products, using the sales tax calculator.
Assumptions and limits
The tool compares two items at a time and assumes both quantities use the same unit. It does not convert units, include delivery, bulk-membership fees or tax, or judge quality. Where a product is sold in different units, convert them yourself before entering the numbers. Retail displays of unit prices are required in some places, but their rounding and units can vary, so use your own calculation for close decisions. To keep track of what you spend monthly, plan it in the budget calculator.
Frequently asked questions
How do I calculate the unit price?
Divide the price by the quantity or size. For example, $4.99 for 500 g is $0.00998 per gram, or about $1.00 per 100 g.
Is the bigger pack always cheaper per unit?
No. Larger packs are often cheaper, but not always, so compare the numbers instead of assuming.
What if the items use different units?
Convert both to the same unit first, such as grams or fluid ounces, then enter the quantities.
Can I use it for non-food items?
Yes. Use it for anything sold in packs: batteries, paper, laundry loads, pet food or printer ink.
Why does the calculator show price per 100 units?
Small unit prices are hard to compare. Per 100 units gives a figure you can read at a glance.