以下のガイドはまだ日本語に翻訳されていないため、英語で表示しています。計算機自体はすべて日本語に対応しています。
この計算機の使い方
- Enter an amount of money in today's terms.
- Enter an average annual inflation rate. Central banks in many economies target about 2%.
- Enter the number of years to see the future cost, and what today's amount will be able to buy then.
計算式
Inflation compounds like interest. Future cost multiplies by the growth factor, and purchasing power divides by it.
Future cost = Amount × (1 + π)^t
Purchasing power = Amount / (1 + π)^t
Cumulative inflation = (1 + π)^t − 1
Example
- $1,000 with 3% average inflation for 10 years.
- Future cost = 1,000 × 1.03^10 ≈ $1,343.92.
- Purchasing power of $1,000 in 10 years ≈ $744.09 in today's money.
よくある質問
Does this use official CPI data?
No. It projects with a constant average rate you enter, which suits planning. Historical inflation varies year to year; for an exact historical comparison, use your national statistics office's official CPI series.
What is a typical inflation rate?
Many central banks, including the US Federal Reserve, the European Central Bank and the Bank of England, target about 2% per year, but actual inflation can be much higher or lower.
How does inflation affect savings?
If your savings earn less than inflation, their real value declines. Compare your after-tax return with inflation to judge real growth.