Inflation Calculator
Inflation works like compound interest in reverse: it does not reduce the number of euros you hold, but what they buy. The calculator runs in four modes — purchasing power of today's money after a number of years, the amount needed in future for today's standard, period inflation from a CPI index, and real return under the Fisher formula. Below are the formulas, worked examples and the practical limitations.
Formula and explanation
Areal = A0 / (1 + π)t | At = A0 · (1 + π)t | rreal = (1 + rnom)/(1 + π) − 1
where: A₀ = today's amount, π = average annual inflation, t = number of years, CPI = consumer price index (NSI), r_nom = nominal return, r_real = real return after inflation.
The inflation calculator shows how inflation eats away the purchasing power of money — it acts like compound interest in reverse. In one direction it calculates what today's money will really be worth in years, and in the other — what amount will be needed in the future for today's standard, which is indispensable for pension and long-term planning. The Fisher formula links inflation to the other calculators, showing the true (real) return on deposits and investments.
Methodology
What the inflation calculator works out
Inflation is the sustained rise in the general price level. Its effect on personal finances runs both ways: it erodes the real value of savings and fixed incomes, and it equally erodes fixed-rate debt. The calculator measures both sides of that process.
Its four modes answer different questions. Purchasing power tells you what today\'s money will be worth after a given number of years, expressed in today\'s prices. Future amount answers the reverse — how many euros you will need in future to maintain the same standard of living. Period inflation from an index derives cumulative and average annual inflation between two readings of the consumer price index. Real return under the Fisher formula shows what survives of your nominal return once inflation has taken its share.
The formulas explained in words
- Purchasing power: A_real = A₀ / (1 + π)^t — today\'s amount divided by the cumulative price factor for the period. The result is in today\'s prices.
- Future amount: Aₜ = A₀ · (1 + π)^t — today\'s amount multiplied by the same factor. The result is in future euros.
- Period inflation from an index: cumulative inflation is CPI_end / CPI_start − 1, and the average annual rate is (CPI_end / CPI_start)^(1/t) − 1.
- Real return under Fisher: r_real = (1 + r_nom) / (1 + π) − 1.
The variables are: A₀ — the amount today; π — average annual inflation as a decimal (3% means 0.03); t — number of years; CPI — the consumer price index published monthly by the National Statistical Institute; r_nom — nominal return before inflation.
Note that the Fisher formula is not a simple subtraction. The common approximation "real return = nominal minus inflation" overstates the answer, and the error grows at higher values. At 6% nominal and 3% inflation the approximation gives 3%, while the exact calculation gives 2.91%.
Worked examples
Purchasing power. You hold €100,000 in cash and average annual inflation runs at 3% for the next 10 years. The factor is 1.03^10 = 1.343916. Real purchasing power is 100,000 ÷ 1.343916 = €74,409.39 in today\'s prices. The money loses 25.59% of what it can buy without a single euro leaving the account.
Future amount. The same €100,000 and the same inflation, question reversed: to buy in 10 years what €100,000 buys today you will need 100,000 × 1.343916 = €134,391.64. Applied to a monthly budget: a household spending €3,000 a month today will need 3,000 × 1.03^15 = €4,673.90 a month in 15 years for the same lifestyle. That is the headline number in retirement planning.
Inflation from an index. The consumer price index stood at 100.0 at the start of the period and 118.5 five years later. Cumulative inflation is 118.5 ÷ 100.0 − 1 = 18.5%, and the average annual rate is (1.185)^(1/5) − 1 = 3.45%. Note that 18.5 ÷ 5 = 3.7% is the wrong answer, because simple division ignores compounding.
Real return. A portfolio returning a nominal 6% a year against 3% inflation earns a real (1.06 ÷ 1.03) − 1 = 2.91%. A deposit at 2.5% against the same inflation earns a real (1.025 ÷ 1.03) − 1 = −0.49%: the balance grows while its purchasing power shrinks.
| Nominal return | Inflation | Real return | Outcome |
|---|---|---|---|
| 6.00% | 3.00% | 2.91% | Real growth |
| 3.00% | 3.00% | 0.00% | Value preserved |
| 2.50% | 3.00% | −0.49% | Real loss |
Practical guidance and the Bulgarian context
For historical calculations, use the official indices of the National Statistical Institute. The NSI publishes two series — the CPI (national consumer price index) and the HICP (harmonised index, comparable across the EU). They differ in coverage and can give different readings for the same period, so always state which one you used. Since Bulgaria joined the euro area in 2026, the HICP is also the measure by which price stability is assessed at euro-area level.
The distinction between headline and personal inflation matters just as much. The index measures an average consumption basket; yours may look nothing like it. A household with a fixed-rate mortgage and no children experiences different inflation from a family paying rent and school fees. If you are planning for a specific goal — education, healthcare, a property purchase — use inflation for that category of goods and services rather than the headline figure.
On tax: Bulgaria taxes nominal income, not real income. The flat 10% rate on individual income applies to the nominal gain, including the part that merely compensates for inflation. Capital gains on shares traded on a regulated EU or EEA market are exempt for individuals, which keeps their real return closer to the nominal figure. For other instruments, check the rates currently in force.
Limitations of the calculation
The calculator assumes a constant average inflation rate across the whole horizon. Real inflation moves in waves and rarely follows an even path, so results over long periods are scenarios rather than forecasts. It is worth running three cases — say 2%, 3% and 5% — and working with the range instead of a single figure.
Calculations for past periods depend entirely on the chosen index and on the start and end dates. Changing the base year or the index methodology changes the numbers. Changes in product quality are not captured either; the indices attempt to adjust for it, but only approximately.
Finally, the Fisher formula is exact only when the nominal return and the inflation rate refer to the same period. Do not set a ten-year expected return against last year\'s inflation — that is the most common misuse of this measure.
Frequently asked questions
How do I calculate the purchasing power of money after several years?
Divide today's amount by (1 + inflation) raised to the number of years. On €100,000 with average annual inflation of 3% over 10 years the factor is 1.343916 and real purchasing power is €74,409.39 in today's prices. That is a 25.59% loss in what the money can buy, even though the nominal amount has not changed.
What is the difference between the NSI's CPI and HICP?
The CPI is the national consumer price index and reflects household spending within the country. The HICP is the harmonised index, compiled on a common EU methodology so that countries are comparable. They cover slightly different baskets and can give different readings for the same period. International comparisons and euro-area price stability assessments use the HICP.
Why is real return not simply nominal minus inflation?
Because return and inflation compound multiplicatively rather than adding up. The exact Fisher formula is (1 + nominal) ÷ (1 + inflation) − 1. At a 6% return and 3% inflation the approximation gives 3% while the exact figure is 2.91%. At low values the difference is small, but at double-digit rates it becomes material and distorts long-term plans.
What average inflation rate should I assume when planning?
There is no single right answer, so work in scenarios. A practical approach is to run three cases — conservative at around 2%, base at around 3%, and a stress case at 5% or more — and check that your plan survives all three. The ECB targets 2% inflation over the medium term, but realised figures deviate considerably in individual years.
Is the inflation component of a return taxed?
Yes. Bulgaria taxes nominal income rather than real income, so the flat 10% rate applies even to the part of a gain that merely compensates for inflation. The exception is the sale of shares and units on a regulated EU or EEA market, which is exempt for individuals. For other instruments, check the rates currently set out in the Personal Income Taxes Act.
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The calculators are for guidance only and do not constitute financial, tax or legal advice. Parameters reflect 2026 legislation and should be verified annually. For a specific case, book a consultation with our specialists.