CPI Inflation Rate Calculator
From the current and previous Consumer Price Index, compute the inflation rate: (CPI_now - CPI_prev) / CPI_prev x 100%.
輸入資料
計算結果
重點速覽：Inflation rate = (current CPI - previous CPI) / previous CPI x 100%. CPI tracks a weighted basket of consumer goods/services; the rate shows how much overall prices rose (positive) or fell (negative = deflation). Example: 110 vs 104 → ≈5.77%. Inflation erodes purchasing power; real return ≈ nominal - inflation. WARNING: CPI is an average basket; personal inflation differs by spending mix; compare on same base/period. Education, not advice.
計算公式
通脹率 = (本期 CPI − 前期 CPI) ÷ 前期 CPI × 100%。
$$通脹率：$Inflation = \dfrac{CPI_{t}-CPI_{t-1}}{CPI_{t-1}}\times100\%$$$$$示例：$\dfrac{110-104}{104}\times100\%\approx5.77\%$$$$$負值代表通縮 (物價下跌)。$$使用說明
- Enter the current period's CPI.
- Enter the previous period's CPI.
- View the inflation rate (positive = inflation, negative = deflation).
由本期與前期 CPI 計算通脹率
| 前期 CPI | 本期 CPI | 通脹率 | 情況 |
|---|---|---|---|
| 104 | 110 | 5.77% | 物價上升 (通脹) |
| 122 | 125.5 | 2.87% | 溫和通脹 |
| 110 | 104 | −5.45% | 物價下跌 (通縮) |
理財情境案例
案例一：計算兩期之間的通脹率
某地區前期 CPI 為 104，本期升至 110。
通脹率 = (110 − 104) ÷ 104 × 100% ≈ 5.77%。
解讀：這段期間整體物價上升了約 5.77%,代表同一筆錢能買到的東西變少了——購買力被通脹侵蝕。若你的收入或投資回報跑不贏這 5.77%,實質購買力其實是下降的。這正是為何理財時要關注『實質報酬 (扣除通脹後的回報)』而非只看名目數字。
案例二：通脹如何侵蝕投資的實質回報
某人投資一年名目回報 5%,同期通脹率 3%。
精確的實質報酬率 = (1 + 5%) ÷ (1 + 3%) − 1 ≈ 1.94%（常用近似值為 5% − 3% = 2%）。
解讀：名目上賺了 5%,但因為物價同時上漲 3%,扣除通脹後實際購買力只增加約 1.94%。這說明評估投資或存款是否『真的賺錢』,一定要把通脹計入——若名目回報等於或低於通脹率，實質購買力便停滯甚至縮水。長期而言，能否跑贏通脹，是理財與資產配置的核心考量之一。⚠️ 本計算器只計算 CPI 通脹率，實質報酬需另行結合你的名目回報計算。
常見問題
What is CPI and how does it measure inflation?
The CPI is an index tracking a weighted basket of representative consumer goods and services over time. Statistical offices survey household spending to set category weights (food, housing, transport, etc.), then track prices monthly and index them (base = 100). The inflation rate is the percentage change between two index values. The basket-average avoids single-item noise but also means personal experience may differ.
How does inflation relate to real return?
Inflation determines your real (purchasing-power) return. Approx: real return ≈ nominal return - inflation (precisely via Fisher: (1+nominal)/(1+inflation)-1). If a deposit yields 4% but inflation is 5.77%, real return ≈ -1.77% — you lose purchasing power. This is why high inflation makes low-interest deposits 'lose money' and why you should look at real, not nominal, returns.
Is inflation always bad? What about deflation?
Moderate, stable inflation (~2% target for many central banks) is healthy — it encourages spending/investment and eases debt burdens. High/uncontrolled inflation erodes savings and distorts prices. Deflation (falling prices) sounds good but risks a deflationary spiral: delayed consumption → weaker demand → job cuts → less demand. Central banks target low, stable positive inflation, not zero.
Where do I find Hong Kong inflation data? What is Composite CPI?
In Hong Kong, the Census and Statistics Department compiles the Composite CPI — a basket of everyday goods/services weighted by household spending, compared across periods to derive the inflation rate. It also publishes Class A/B/C CPI for lower/middle/higher-spending households, and 'underlying inflation' strips out one-off government relief. For authoritative figures, visit the C&SD website.
Why does inflation feel higher than the official rate?
Because everyone's basket differs from the average, plus psychological and frequency biases. If you spend heavily on fast-rising items (rent, dining), your personal inflation exceeds the composite. High-frequency purchases amplify the feeling; one-off subsidies lower the official figure you may not feel. Check the CPI class closest to your spending, or track your own basket.
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參考資料
內容審核：香港計算器財經團隊。計算邏輯與公式參考香港金融管理局（HKMA）及投資者及理財教育委員會（IFEC）之個人理財計算指引，結果僅供參考，實際以相關機構公佈為準。