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Unit Price Calculator: Compare Price per Ounce, Pound, 100 g or Liter

Type the price and size of two to four products and see which one is cheaper per ounce, per 100 g, per liter or per item. It converts between US and metric units for you, so a 16 oz jar and a 500 g jar compare fairly.

By Suman Sharma · Updated

Unit price · which is cheaperLocal
  1. Item A
    $
    ×

    $0.218 per oz · 9.0% more

  2. Item B
    $
    ×

    $0.200 per oz · Best value

Best value
Item B
$0.200 per oz. The priciest costs 9.0% more per unit.

How to use this tool

  1. Enter each product

    Type the shelf price and the size printed on the pack, then pick its unit: g, kg, oz, lb, ml, L, fl oz, gallons or items.

  2. Add the pack count for multipacks

    For a 6 × 330 ml pack, enter 330 ml and ×6. The price is for the whole multipack.

  3. Pick how to compare

    Choose per oz, per lb, per 100 g, per kg, per liter or per item. The best value is highlighted and the others show how much more they cost.

Example

Three sizes of peanut butter, including a 2-pack.

Input

  • A: 16 oz jar for $3.48
  • B: 40 oz jar for $7.98
  • C: 2 × 28 oz jars for $11.96
  • Compare: per lb

Result

  • A: $3.48 per lb (9.0% more)
  • B: $3.19 per lb · Best value
  • C: $3.42 per lb (7.1% more)

The twin pack holds the most peanut butter but isn't the cheapest per pound. Bigger packs and multipacks are often priced for convenience, not value, which is exactly what this check catches.

Why the shelf tag isn't always enough

Many US stores print a unit price on the shelf tag (a few states require it), and in the EU and UK it's required by law. But tags don't always use the same unit for every product on the shelf. One brand might show price per ounce and the next price per count, and a promotional price often isn't reflected in the unit price at all.

Working it out yourself takes the guesswork away, especially when you're comparing a sale price, a club-store bulk pack, or an online listing against what's in the store.

How unit price is calculated

Unit price is the price divided by the amount. To compare two products sold in different units, both are converted to the same base first: grams for weight, milliliters for volume. This calculator uses exact conversions: 1 oz is 28.3495 g, 1 lb is 453.592 g, 1 US fl oz is 29.5735 ml and 1 US gallon is 3.785 liters.

  • Weight: g, kg, oz, lb.
  • Volume: ml, L, US fl oz, US gallons.
  • Count: items, for things like eggs, diapers, dishwasher tabs or trash bags.

When the cheapest unit price isn't the best buy

  • Waste: a bigger pack is only cheaper if you use it before it goes off.
  • Storage: a 10 lb bag of rice is a bargain only if you have somewhere to keep it.
  • Quality: store brands and name brands aren't always the same product, so compare what you'd actually be happy to buy.
  • Cash flow: bulk buying ties up money now for savings later.

Conversions used

  • 1 oz = 28.3495 g, so 100 g ≈ 3.53 oz
  • 1 lb = 16 oz = 453.592 g
  • 1 kg = 2.2046 lb
  • 1 US fl oz = 29.5735 ml
  • 1 US gallon = 128 US fl oz = 3.785 L
  • 1 L ≈ 33.8 US fl oz
  • Fluid ounces measure volume and ounces measure weight, so don't compare a 16 fl oz drink with a 16 oz jar of something solid.

Shopping tips

  • Compare per 100 g or per oz across brands, not per pack.
  • Check multipacks: a 2-pack is sometimes dearer per unit than two singles on sale.
  • Watch for shrinkflation: a smaller pack at the same price is a price rise. The unit price shows it immediately.
  • Online listings often quote a unit price on a different basis from the store; recalculate before you compare.

Common errors

  • Comparing weight with volume

    Ounces (weight) and fluid ounces (volume) aren't the same thing. If one bottle says 16 fl oz and another 500 g, the tool flags it. Use the same kind of unit on every item.

  • Forgetting the pack count

    For a 12-pack of 12 fl oz cans, enter 12 fl oz and ×12. Leaving the count at 1 makes the multipack look 12 times more expensive.

  • Using the regular price during a sale

    Enter what you'll actually pay at the register. A 'buy 2, get 1 free' deal means three packs for the price of two: enter the price of two and ×3.

  • Mixing up the net and drained weight

    Canned fruit and vegetables often list both. Compare drained weight if you'll pour the liquid away, and use the same figure for every can.

Frequently asked questions

How do I calculate price per ounce?

Divide the price by the number of ounces. A 12 oz bag for $8.99 is about $0.75 per ounce. If the size is in grams, divide grams by 28.35 to get ounces first, or let the calculator convert it.

Is the bigger size always cheaper?

No. Stores often price large and multipack sizes for convenience, and sales on smaller sizes can flip the result. That's why it's worth checking the unit price every time instead of assuming.

How do I compare a US size in ounces with a European size in grams?

Pick the unit on each item exactly as printed on the pack, then compare per 100 g or per oz. The calculator converts both to the same base, using 1 oz = 28.3495 g.

Does it work for liquids and things sold by count?

Yes. Use ml, liters, US fl oz or gallons for liquids, and items for products sold by count like eggs, diapers or dishwasher tablets.

How do I calculate price per 100 grams?

Divide the price by the weight in grams and multiply by 100. A 400 g pack for $3.20 is $0.80 per 100 g.

What is shrinkflation?

When a product gets smaller but keeps the same price, so you pay more per unit without noticing. Comparing unit prices over time reveals it.

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