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How to calculate shrinkflation

How to calculate shrinkflation. Use the relevant ShopWithShery calculator to verify the math with your own prices, quantities and terms.

Updated August 9, 2026 · Source-backed where consumer guidance is referenced
Short answer

Calculate old price per unit and new price per unit. The percentage change between those two unit prices is the effective price increase, even when the shelf price barely changes.

The calculation to use

Unit-price change % = (new price/new size ÷ old price/old size − 1) × 100

Watch for: Use the same unit of measure for both packages before comparing.

A practical way to compare the offers

  1. Write down the price, quantity, package size and promotion exactly as shown.
  2. Convert both choices to the same comparison basis: per unit, delivered cost, effective discount or cost per use.
  3. Separate immediate checkout savings from later rewards such as cashback or store credit.
  4. Consider waste, required purchase quantity, recurring commitments and return restrictions.
  5. Choose the offer that fits both the math and the quantity you will realistically use.

Why shoppers get this wrong

Retail offers often present several numbers at once: package size, headline discount, multibuy quantity, loyalty reward and shipping threshold. Human comparison becomes difficult when those numbers use different denominators. Normalizing the offers removes much of that noise.

Use the calculator

Calculate shrinkflation using the quantity or usage that actually matters.

Shrinkflation Calculator →

Sources and verification

These sources support the consumer-shopping principles discussed on this page. Your own retailer's current offer and policy still control the actual transaction.

NIST SP 1181 — Unit Pricing Guide, 2025 EditionNational Institute of Standards and Technology · verified 2026-08-09Official U.S. best-practice guide for unit pricing; updated May 20, 2026.Uniform Unit Pricing: Tools for Consumers to Fight ShrinkflationNational Institute of Standards and Technology · verified 2026-08-09Official consumer explanation of unit pricing and shrinkflation.

Continue the shopping decision

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