Use the Shrinkflation Calculator to compare old and new unit prices, measure the hidden effective increase, and find a fair package price or quantity.
Shrinkflation Formula
Shrinkflation is measured by comparing the old and new unit prices. Divide each package price by its quantity:
U_old = P_old / Q_old U_new = P_new / Q_new
The effective price change is the percentage change between those two unit prices:
Effective change = (U_new / U_old - 1) * 100%
The calculator can also find the fair new price or quantity that would preserve the old unit value:
Fair new price = U_old * Q_new Fair new quantity = P_new / U_old
Variables:
- U_old is the old price per unit of quantity
- U_new is the new price per unit of quantity
- P_old and P_new are the old and new package prices
- Q_old and Q_new are the old and new package quantities
Use the same quantity unit for both packages. The quantity may be ounces, grams, milliliters, pounds, sheets, pods, rolls, or any other consistent unit. The effective change captures a visible price change and a hidden size change in one result.
Shrinkflation Examples
The table shows why comparing shelf prices alone can be misleading. A package may cost the same or even slightly less while its price per unit rises.
| Old package | New package | Sticker-price change | Effective unit-price change |
|---|---|---|---|
| $5.00 for 16 oz | $5.00 for 14 oz | 0.00% | +14.29% |
| $4.00 for 12 oz | $4.40 for 11 oz | +10.00% | +20.00% |
| $6.00 for 24 oz | $5.75 for 20 oz | -4.17% | +15.00% |
| $3.60 for 18 units | $3.60 for 15 units | 0.00% | +20.00% |
| $8.00 for 32 oz | $8.40 for 32 oz | +5.00% | +5.00% |
Example Problems
Example 1: Same price, smaller package.
A product used to cost $5.00 for 16 ounces and now costs $5.00 for 14 ounces. The old unit price was $0.3125 per ounce and the new unit price is about $0.3571 per ounce:
Effective change = ($0.3571 / $0.3125 – 1) * 100% = 14.29%.
Although the shelf price did not change, the effective price increased by approximately 14.29 percent.
Example 2: Find the value-preserving new price.
A 20-ounce package formerly cost $6.00, or $0.30 per ounce. The replacement package contains 17 ounces. At the old unit value, its fair price is $0.30 * 17 = $5.10. A higher shelf price represents an effective increase; a lower price represents a unit-value decrease.
Frequently Asked Questions
What is the difference between inflation and shrinkflation?
Ordinary price inflation is visible when the price rises for the same quantity. Shrinkflation occurs when the quantity falls, sometimes with little or no change in the displayed price. Both raise the unit price, which is why a unit-price comparison captures either case.
Does the calculator work when both price and size change?
Yes. Enter both the old and new price and quantity. The formula compares unit prices, so it measures the combined effect even when the package becomes smaller while the shelf price rises or falls.
Should I compare weight, volume, or item count?
Use the measure that best represents what you receive and keep it consistent between packages. Compare ounces with ounces, grams with grams, milliliters with milliliters, or counts with counts. Quality changes, concentration changes, coupons, and taxes require separate judgment and are not captured by quantity alone.
