How this number is made
The bigger pack is not automatically the better price. Divide each price by its quantity. The lower price per unit is the cheaper buy, before you consider food you will throw away.
- Convert both quantities into one unit first. Grams and kilograms cannot share a form until you pick one.
- Use the price you will pay, after a discount that actually applies to that pack.
- If you will not use the larger pack, the lower unit price can still be the more expensive choice.
Formula
Unit price = price ÷ quantity. Gap = difference ÷ the higher unit price.
Worked example
€2.40 for 500 grams is €0.0048 a gram. €4.10 for 1,000 grams is €0.0041 a gram. The second pack is cheaper per gram, by about 14.6%.
Questions
What if one label is liters and the other is milliliters?
Convert before you type. 1 liter is 1,000 milliliters. The form will not guess which unit you meant.
Does this include a loyalty discount?
Only if you type the price after that discount. A coupon that fails at the register is not a lower unit price.