What the Inflation Rate Calculator Does
This calculator measures how much prices have risen between two points in time and converts that change into an average annual inflation rate. Inflation is a universal economic concept (not specific to any one country), so you can use any price index or cost figure — a Consumer Price Index reading, the price of a basket of goods, a salary, or the cost of a single product — as long as both values are measured in the same currency or index.
You enter four things: the Start Year, the Start Value, the End Year, and the End Value. The tool returns the average annual (compound) inflation rate, the total percentage change over the whole period, and the number of years between your two dates.
The Formula Explained
The average annual inflation rate is calculated using the compound growth formula rearranged to solve for the rate:
Average Inflation Rate = ((Pf / Pi)1/n − 1) × 100%
- Pi = the start value (initial price)
- Pf = the end value (final price)
- n = number of years (End Year − Start Year)
The calculator also computes the simple total change = ((End Value − Start Value) / Start Value) × 100%. If the number of years is zero or negative, or if either value is zero or negative, the tool safely returns 0 to avoid invalid maths.
Worked Example
Suppose a basket of goods cost 100 in 2010 (Start Value, Start Year) and 140 in 2020 (End Value, End Year). The number of years is 2020 − 2010 = 10.
- Total change = ((140 − 100) / 100) × 100% = 40%
- Average annual rate = ((140 / 100)1/10 − 1) × 100% = (1.40.1 − 1) × 100% ≈ 3.42% per year
So although prices rose 40% in total, the steady compound rate that produces that result is about 3.42% each year.
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輸入各項數值時請務必確認量綱（例如小時、天數、金額、百分比），避免單位不匹配引發推算偏差。
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建議針對極端值與多組預期情景分別試算，觀察輸出數據的波動區間，輔助做出更穩健的決策。
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