How Much Did the Price Per Ounce Increase?
When a package changes, the shelf price alone does not show the full price change. You need the old and new unit prices to see how much each ounce costs.
The shrinkflation calculator compares old package price and size against new package price and size, then shows the unit-price increase.
The Simple Formula
Old unit price = old price / old package size
New unit price = new price / new package size
Unit price increase = (new unit price - old unit price) / old unit price
Generic Example
This example uses hypothetical package versions only. The same method works for weight units, volume units, and count units when the unit family matches.
| Version | Price | Package size | Unit price | Comparison result |
|---|---|---|---|---|
| Old package | $3.00 | 20 oz | $0.1500 per oz | Baseline unit price |
| New package | $3.50 | 18 oz | $0.1944 per oz | About 29.6% higher per ounce |
The new package costs more and contains less, so the price per ounce rises faster than the shelf price suggests.
Common Traps
- Ounce vs fluid ounce: ounces measure weight, while fluid ounces measure volume.
- Old size vs new size: compare the actual package amount, not the front-label design.
- Rounded shelf labels: use the exact package size when you can.
- Sale tags: compare the final price you would pay.
- Multipacks: multiply package count by size per package before dividing by price.
Related calculators
Next guide
If the shelf price stayed the same but the package got smaller, compare the hidden unit-price change directly.