Reduce every package to the same basis
Example: cereal boxes
Box A: $4.79 for 425 g → $1.127/100 g
Box B: $6.49 for 650 g → $0.998/100 g
Box C: 2 × 300 g for $6.00 → $1.00/100 g
Box B and the multipack are nearly equal by unit price. Box B is slightly lower; Box C divides into two sealed packages, which may preserve freshness better.
Look past family, value, club, and jumbo
Size names are marketing descriptions, not standardized units of value. A ‘family size’ package can be smaller than another brand’s regular package. Compare the printed net quantity and unit price.
Multipack notation needs multiplication. Twelve 355 mL cans contain 4.26 L; six 710 mL bottles also contain 4.26 L. The packaging format may affect storage and waste, but total volume is equal.
| Package | Total quantity | At $6.99 |
|---|---|---|
| 12 × 355 mL | 4.26 L | $1.64/L |
| 6 × 710 mL | 4.26 L | $1.64/L |
| 24 × 355 mL | 8.52 L | $0.82/L |
Concentrated and ready-to-use products
A concentrated product may make more usable volume than its package size suggests. Compare the dilution or dose instructions only when the products perform the same job. Do not invent an equivalent serving size from front-of-package claims.
For drained or prepared foods, decide whether net, drained, or prepared quantity matches how you use the product. Keep the comparison method consistent across both packages.
Use a four-column decision
| Package | Unit price | Usable amount | Cash today |
|---|---|---|---|
| Small | $1.18/100 g | All 400 g | $4.72 |
| Large | $0.92/100 g | Estimated 700 g of 1 kg | $9.20 |
| Large adjusted for use | $9.20 ÷ 700 × 100 | $1.31/100 g consumed | $9.20 |
Sources
Official sources were retrieved on August 27, 2026. Retailer and government guidance can change.