Unit Price Calculator
Free unit price calculator — divide price by quantity to find the cost per unit. Lets you compare grocery deals across different sizes. Runs in your browser.
Type the price and the quantity. The calculator returns the unit price — how much you pay per gram, ounce, millilitre, roll, sheet, or whatever unit you measured the quantity in.
The formula
unit price = price ÷ quantity
A $5 block of cheese weighing 250 g costs 5 ÷ 250 = $0.02 per gram.
How to compare two products
Calculate the unit price of each. Pick the smaller number.
- A 250 g pack at $5.00 → $0.020/g
- A 500 g pack at $8.00 → $0.016/g ← cheaper
The 500 g pack is the better deal per gram, even though the sticker price is higher. Most grocery shelves print this number on the tag (legally required in many places), but it’s not always there for the smaller items or for sale-priced products.
Pitfalls
- Mismatched units. Don’t compare $/g against $/oz. Convert both to the same unit first.
- Spoilage. A bigger pack is only cheaper if you actually use it all — divide by what you’ll use, not the package size.
- Quality differences. Unit price treats two items as equivalent. For fungible goods (rice, salt, paper towels) that’s fine; for things where quality matters a lot, factor that in.
Where unit pricing helps most
- Grocery comparison (cheese, rice, paper towels, cleaning products).
- “Family size” vs. “regular” decisions where the marketing implies savings.
- Bulk online deals — the price-per-unit isn’t always shown next to the bundle price.
Worked examples
-
$5 for 250 g of cheese → cost per gram
Unit price: $0.02 per unit.
-
$12 for 6 rolls of paper towel → cost per roll
Unit price: $2.00 per unit.
Frequently asked questions
How do I compare two products?
Calculate the unit price of each and pick the smaller number. "$5 for 250 g" → $0.020/g; "$8 for 500 g" → $0.016/g — the 500 g pack is cheaper per gram, even though the sticker price is higher. The supermarket-shelf "unit price" tag does this for you (where required by law), but the math is just price ÷ quantity.
What's the \"unit\"?
Whatever you measure quantity in: grams, ounces, millilitres, sheets, pills. The calculator doesn't know — it just divides. So you must use the same unit on both items you're comparing. Don't divide $5/250 g by $8/oz — convert first.
Bigger is usually cheaper per unit, right?
Usually but not always. Larger packs often have a lower unit price, but "family size" and "value" labels can be misleading — sometimes the medium-sized item is actually cheapest per unit. Always check, especially on items the supermarket promotes heavily.
What about brands and quality?
Unit price is just the math. If the cheaper option is also worse (less filling, lower quality, wasteful packaging), unit price alone isn't the whole story. But for fungible goods (rice, sugar, paper towels) it's the dominant signal.
Does shelf life matter?
Yes, if you might throw some away. A 5 kg bag at $0.50/kg sounds cheaper than 1 kg at $0.80/kg, but if you waste 2 kg of the big one, your effective unit price is $1.25/kg. Adjust for realistic usage.