Price divided by size, then compare the smallest
Unit price strips out the package size so two products become directly comparable. A gallon of milk costs more than a quart, but at $0.035 an ounce versus $0.040 an ounce the gallon is the better buy. The shelf tag usually prints this in small type under the main price; when it is missing, divide it yourself.
The bigger size is not always cheaper per ounce
Usually bulk wins, but tiered pricing quietly reverses it often enough to be worth checking. Here the mid size beats the jumbo per ounce.
Same product, three sizes. The 40 oz is cheapest per ounce; the 64 oz "value" tub is actually dearer than the 40 oz. Only the unit price shows this.
What trips up a size comparison
- Waste on perishables. A bulk pack you bin before finishing costs more per ounce used, not less. Match the size to how fast you get through it.
- Brand vs. size. A store brand in a small pack often beats a name brand in bulk. Compare the unit price, not the label.
- Shrinkflation. Same price, quietly smaller pack. Coffee dropping 12 oz to 10 oz is a hidden 20% rise per ounce even though the price tag never changed.
- Per 100 g labels. Some products list price per 100 g or 100 ml. To match a US per-ounce figure, convert one side so both use the same base.
Common questions
How do I work out unit price?
Divide the total price by the quantity in the package. A 32 oz jar at $5.99 is 5.99 divided by 32, or about 18.7 cents per ounce. Do the same for each size and the smallest number wins.
Is the bigger size always cheaper per unit?
No. Larger packs often cost less per unit, but not always. Tiered pricing sometimes makes the big size dearer per ounce, a name brand can lose to a smaller store brand, and any bulk perishable you throw away wipes out the saving.
How do I compare products sold in different units?
Convert both to the same unit first. To compare a jar priced per ounce with one priced per gram, use 1 oz = 28.35 g, or just get both down to price per 100 g. Mixing ounces and grams is the most common mistake.
