Compare packages fairly by dividing total price by net mass. Animated packages and equal-mass comparisons distinguish dollars per gram from cents per gram.
Open the price per gram calculator · More Finance videos
The calculation
Price per gram = total price ÷ mass in grams
Worked example
A $6 package containing 250 g costs $0.024/g, or 2.4¢/g. A $9 package containing 400 g costs $0.0225/g, or 2.25¢/g. Per 100 g, those prices are $2.40 and $2.25. At 400 g, the second rate saves $0.60.
Use the same mass units and a consistent price basis, including applicable discounts or charges. Lower unit price does not by itself establish quality or suitability.
Video chapters
- 0:00 — Cheaper package or cheaper per gram?
- 0:14 — Convert the mass to grams
- 0:27 — $6 ÷ 250 g = $0.024/g
- 0:41 — $9 ÷ 400 g = $0.0225/g
- 0:54 — Compare at 100 grams
- 1:07 — Check the difference at 400 grams
- 1:21 — Compare equivalent contents and costs
- 1:39 — Total price ÷ grams
Read the full transcript
One package costs six dollars for two hundred fifty grams. Another costs nine dollars for four hundred grams. The first has the lower price tag. But which gives the lower cost for the same amount? Price per gram puts both packages on one scale.
Before dividing, use the same mass unit for both packages. One kilogram is one thousand grams, so zero point four kilograms is four hundred grams. Use the product's net amount when comparing contents. Packaging weight is a different quantity.
For the first package, divide six dollars by two hundred fifty grams. The result is zero point zero two four dollars per gram. In cents, that is two point four cents per gram. Keep the currency label visible: dollars and cents differ by a factor of one hundred.
For the second package, nine dollars divided by four hundred grams is zero point zero two two five dollars per gram, or two point two five cents. That is the lower unit price, even though the package costs more at checkout.
Tiny per-gram numbers can be easier to compare at one hundred grams. Multiply each by one hundred: the prices become two dollars forty cents and two dollars twenty-five cents per hundred grams. The difference is fifteen cents for the same hundred-gram amount.
At four hundred grams, the first unit price would cost nine dollars sixty cents. The second costs nine dollars. The difference is sixty cents for that matched quantity. Use unrounded values in intermediate steps so an early rounding choice does not erase a small price difference.
A unit price compares quantity, not every aspect of value. Check that the products are comparable, and treat shipping, taxes, discounts, and usable contents consistently. Buying a larger package is only useful if the additional quantity is useful to you; a lower unit price is not the whole decision.
Convert the mass to grams, divide the total price by that mass, and compare the same currency per gram. Multiply back to check the total. In this example, the four-hundred-gram package has the lower unit price: two point two five cents per gram.