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Shrinkflation Calculatorの包括的な教育ガイドを準備中です。ステップバイステップの解説、数式、実例、専門家のヒントをお届けしますので、もうしばらくお待ちください。
The Shrinkflation Calculator quantifies the hidden price increase when a product's package shrinks but its price stays the same — a stealth strategy manufacturers use to maintain price points during inflation while reducing per-unit value. Calculator computes old price-per-unit, new price-per-unit, and the effective percentage increase. Classic examples: cereal box dropping from 16 oz to 14 oz at the same price = 12.5% effective price increase; toilet paper rolls going from 264 sheets to 244 sheets = 7.6% increase; chip bag dropping from 10 oz to 9 oz = 10% increase. Shrinkflation appears across consumer packaged goods: cereals, snacks, ice cream, frozen pizza, candy bars, paper products, cleaning supplies, even pet food. Pringle's chips went from 5.2 oz to 5.0 oz (4% increase) in 2022. Folgers coffee went from 51 oz to 43.5 oz (17% increase). Wheat Thins went from 9.1 oz to 8.5 oz (7% increase). Researchers at the Federal Reserve estimate shrinkflation accounted for ~8% of effective grocery inflation during 2020–2023, partially explaining why CPI measurements understate consumer experience. Formula: Effective Increase % = ((New $/Unit − Old $/Unit) / Old $/Unit) × 100. This is the price increase felt per actual quantity of product purchased — different from sticker price comparison which would show 0% change. The calculator outputs both old and new per-unit prices alongside the effective increase to make the math transparent and verifiable. Who benefits from awareness: home shoppers who can switch to store brands (typically the least affected by shrinkflation), batch buyers who lock in current sizes, and consumer advocates documenting industry patterns. The grocery industry argues shrinkflation is preferable to sticker shock because consumers psychologically prefer 'same price, slightly less' over 'same amount, higher price.' Critics counter that this is deceptive — most shoppers don't notice 5–10% size changes but would notice equivalent price increases. Mandatory disclosure laws (France's 'shrinkflation labels' since 2024) require retailers to flag products that shrank.
- 1Step 1 — Enter old size and old price (check old packaging, archive.org for past listings, or shrinkflation databases)
- 2Step 2 — Enter new size and new price (current store shelf)
- 3Step 3 — Select unit (oz, g, mL, count — make sure both sizes use the same unit)
- 4Step 4 — Calculator computes old $/unit = Old_P / Old_S and new $/unit = New_P / New_S
- 5Step 5 — Computes effective increase = ((New $/unit − Old $/unit) / Old $/unit) × 100
- 6Step 6 — Computes size reduction percentage for reference
- 7Step 7 — Output labels result as Within Inflation Range or Likely Shrinkflation
Classic shrinkflation — package look similar, price unchanged, but per-ounce cost rose 14.3%.
Common pattern in paper products; size reduction often visible only on side panel of package.
Combination: smaller container + higher price = compound increase
Both size and price moved against consumer — increase is multiplicative not additive.
Same size, higher price — visible to shoppers. Not shrinkflation; ordinary inflation passed through.
Grocery shopping awareness
Brand vs store-brand comparison
Inflation analysis (true cost of living)
Consumer advocacy documentation
Personal CPI tracking for budget planning
Investigative journalism on packaged goods industry
Is shrinkflation always bad?
It's a hidden price increase — bad for consumers who don't notice but often preferable to sticker shock for manufacturers managing input cost increases. Buying store/generic brands typically avoids the worst examples because these brands optimize for value rather than price-point maintenance. Bulk-buying clubs (Costco, Sam's) also tend to maintain sizes since their value prop is price-per-unit.
How do I track which products shrank?
Several databases crowdsource shrinkflation: r/shrinkflation on Reddit, the Consumer Watch shrinkflation tracker, and Mouse Print* by Edgar Dworsky (the original shrinkflation journalist). Archive.org's Wayback Machine often has old product pages. Some packaging includes 'now [smaller size]' or 'redesigned package' as oblique signals.
Are price-per-unit shelf tags reliable?
Generally yes — most US states require retailers to display unit pricing (per oz, per sheet, per ounce). Always check $/oz tags rather than total price. European countries similarly require unit pricing. The unit price catches both shrinkflation AND straight price increases, making it the single most useful consumer tool.
What about premium-ization (smaller package marketed as 'snack-size')?
Common adjacent strategy — manufacturer reduces size and rebrands as a 'snack pack' or 'lunch portion' at the same or higher price. Unit price reveals the math: a 'snack-size' 1 oz at $1.50 is $1.50/oz; the regular 5 oz at $4 is $0.80/oz. Convenience premium can be 50–100% higher per oz.
Does inflation explain all shrinkflation?
Partly. Input costs (wheat, oil, plastic, packaging) did rise significantly in 2020–2023. But Federal Reserve research found shrinkflation persisted after input costs normalized in 2024, suggesting some of it is permanent margin expansion rather than temporary inflation adjustment. The line between necessary cost pass-through and opportunistic margin expansion is murky.
プロのヒント
Always check $/oz or $/gram unit pricing tags on grocery shelves rather than total price — required unit pricing is the single most useful consumer tool for catching both shrinkflation and straight price increases. Most stores display these prominently; phone calculators handle the math when they don't.