Inflation is the slow, steady rise in the general level of prices, and its most important consequence is that a fixed sum of money buys less as time passes. The 100 in your pocket today will not command the same basket of goods in ten years, because the price tags on nearly everything - groceries, rent, fuel, services - tend to drift upward. Understanding inflation is not an academic exercise: it decides whether your savings are actually growing, how much you need to retire, and whether a pay rise is a real gain or just running to stand still. This guide explains the two calculations at the heart of inflation - what an amount will cost in future and what today's money will be worth - and shows how to use them with the Inflation Calculator to plan realistically.
The future-cost formula
Inflation compounds in exactly the way interest does, just working against you. If prices rise by a steady rate each year, the future cost of something that costs a certain amount today is found by compounding that amount forward:
- Future cost = Present amount × (1 + r)^n
- Present amount is what the item or basket costs today.
- r is the annual inflation rate, written as a decimal (6% becomes 0.06).
- n is the number of years into the future.
The exponent is what makes inflation deceptively powerful. Because each year's prices rise on top of the previous year's already-raised prices, the cost curve bends upward rather than climbing in a straight line. A rate that sounds modest in a single year - 6%, say - stacks up to a very different number across a decade or a working lifetime.
The purchasing-power formula
The flip side of rising prices is falling purchasing power: what a fixed amount of money can actually buy shrinks over time. To find the future purchasing power of a sum you hold today, you divide instead of multiply:
- Future value of today's money = Present amount / (1 + r)^n
This tells you what a nominal amount will really be worth once inflation has eaten into it. It is the calculation that matters for anyone holding cash, a fixed pension, or a savings balance that is not keeping pace with prices - the number on the statement stays the same, but the groceries it buys keep shrinking. The Inflation Calculator reports both directions at once: the future cost of an amount and what that amount will be worth in tomorrow's money.
A worked example
Suppose something costs 1,00,000 today and inflation runs at a steady 6% a year. Over 10 years:
- Future cost = 1,00,000 × (1.06)^10 ≈ 1,79,085.
- Purchasing power of today's 1,00,000 = 1,00,000 / (1.06)^10 ≈ 55,839.
So the same item that costs 1,00,000 now will cost about 1,79,085 in a decade - it has risen by almost four-fifths. Read the other way, the 1,00,000 you hold today will buy only about 55,839 worth of goods in ten years' time; more than 44% of its purchasing power has quietly evaporated. Stretch the horizon further and the effect compounds harder: 50,000 held for 25 years at 7% inflation would need to grow to about 2,71,372 just to buy the same things, and left as idle cash it would be worth only about 9,212 in today's terms. Enter your own amount, rate and number of years in the Inflation Calculator to see both figures instantly.
Why real returns matter more than headline returns
The most important lesson inflation teaches is to judge an investment by its real return - the growth left over after inflation - rather than its headline, or nominal, return. The relationship is not a simple subtraction. The precise real return is:
- Real return = (1 + nominal rate) / (1 + inflation rate) − 1
If an investment earns a nominal 10% while inflation is 6%, a quick subtraction suggests a 4% real gain - but the exact figure is (1.10 / 1.06) − 1 ≈ 3.77%. The subtraction shortcut is close enough for rough work and always slightly optimistic, but the point stands: a savings account paying 6% during 6% inflation earns you nothing in real terms, and anything paying below the inflation rate is quietly losing you money even as the balance ticks up. This is why holding large sums as idle cash is rarely a neutral choice - it is a slow, guaranteed erosion.
How much does inflation halve your money?
A useful shortcut for gauging inflation's speed is the Rule of 70: divide 70 by the annual inflation rate to estimate how many years it takes for prices to double - and equivalently for the value of cash to roughly halve. At 6% inflation, 70 / 6 ≈ 11.7 years, which matches the exact figure of about 11.9 years closely enough for planning. At 3% it takes roughly 23 years; at 10%, just 7. The rule turns an abstract percentage into a concrete timeline and is a fast sanity check on any long-range plan, from a retirement target to the future price of a house or a child's education.
Planning around inflation
Because inflation is relentless and compounding, the practical response is to make sure the money you are relying on for the future grows faster than prices. Three habits help. First, set financial goals in future rupees, not today's - if you want the buying power of 50,000 a month in retirement thirty years out, size the target using the future-cost formula, not the sticker figure. Second, favour assets whose long-run returns have historically outpaced inflation over holding large balances in low-yield cash. Third, revisit your assumptions periodically, since inflation rates shift and a plan built on last decade's numbers can drift. Whenever you need to convert between today's money and tomorrow's - or check whether a return is really beating inflation - run the numbers through the Inflation Calculator so your plan is anchored to real purchasing power rather than nominal amounts.
Frequently asked questions
- How do I calculate the future cost of something due to inflation?
- Use Future cost = Present amount × (1 + r)^n, where r is the annual inflation rate as a decimal and n is the number of years. For example, an item costing 1,00,000 today with 6% inflation will cost 1,00,000 × (1.06)^10 ≈ 1,79,085 in ten years. Inflation compounds, so each year's prices rise on top of the previous year's, which is why the cost climbs faster than a simple year-times-rate estimate would suggest.
- What happens to the purchasing power of my savings under inflation?
- Purchasing power falls, because the same money buys fewer goods as prices rise. The future value of today's money is Present amount / (1 + r)^n. At 6% inflation, 1,00,000 held as cash for 10 years will buy only about 55,839 worth of goods in today's terms - a loss of more than 44% of its value - even though the number on the statement never changes.
- What is a real return and why does it matter?
- A real return is the growth of an investment after inflation, calculated as (1 + nominal rate) / (1 + inflation rate) − 1. A nominal 10% return with 6% inflation gives a real return of about 3.77%, not the 4% a simple subtraction suggests. It matters because only the real return grows your actual buying power - an account paying below the inflation rate is losing you money in real terms even as the balance rises.