How to Compare Mixed Units Without Misleading Math
Two prices are comparable only when their quantities describe the same kind of measurement on the same scale. A shelf label showing dollars per pound cannot be compared directly with one showing dollars per ounce. Converting first prevents a 16-to-1 scale difference from looking like a bargain.
Ounces and pounds
One pound contains 16 ounces. For 16 oz at $4.80 and 1.5 lb at $6.72, convert 1.5 × 16 = 24 oz. The first is $4.80 ÷ 16 = $0.30/oz. The second is $6.72 ÷ 24 = $0.28/oz, so the 1.5 lb package is lower by two cents per ounce.
You can instead convert 16 oz to 1 lb and compare $4.80/lb with $4.48/lb. Either common basis produces the same winner.
Grams and kilograms
One kilogram contains 1,000 grams. A 600 g bag at $3.90 costs $0.0065 per gram, or $0.65 per 100 g. A 1 kg bag at $6.20 costs $0.0062 per gram, or $0.62 per 100 g. Expressing both per 100 g makes the three-cent difference easier to read without changing it.
Milliliters and liters
One liter contains 1,000 mL. A 750 mL bottle at $3.15 costs $4.20/L. A 1.5 L bottle at $6 costs $4/L. The larger bottle is lower by 20 cents per liter. U.S. fluid ounces, cups, pints, quarts, and gallons can also be converted by volume; the calculator uses U.S. liquid measures.
Measurements that should not be compared directly
Weight ounces and fluid ounces are not interchangeable. Weight describes mass; fluid ounces describe volume. Converting between weight and volume would require a product’s density, which this site does not guess. A gram-versus-milliliter comparison has the same problem.
Counts also require meaning. One roll is not equal to one sheet, and one bottle is not a fixed volume. If two paper products list sheets per roll, compare sheets. If two drinks list bottle volume, compare volume.
U.S. and metric weights, and U.S. and metric lengths, are separate calculator groups. Convert externally only when the package facts give you a reliable basis. Never treat the numeric labels as comparable just because both are measurements.
Enter mixed units in Compare Deals
In Compare Deals, choose the unit printed for each package. Compatible units normalize automatically, and incompatible categories produce a warning instead of a winner. The results display all prices using Deal A’s unit so the comparison stays on one scale.
Read the methodology for the exact conversion factors and rounding rule, or see the worked examples for a 16 oz versus 1.5 lb calculation.