One investment, two different percentages
A dollar-priced asset rising 20% does not mean that someone investing Turkish lira earned exactly 20%. The dollars purchased initially and their lira value at the end also matter. Consequently, USD and TRY charts can describe different percentage changes for the same holding. Neither automatically invalidates the other. They measure the investment in different units. Start by deciding which currency answers your question, particularly if the future expense you are saving for uses a specific currency.
This is a calculation guide, not an exchange-rate forecast or historical performance report. Every price and exchange rate below is hypothetical. The review date, 14 September 2026, does not turn those numbers into current quotes. The examples omit taxes, dealing spreads, commissions and interest on cash. These omissions make the arithmetic visible, but they also mean the output is not a personal net return or proof that purchasing power increased.
Work through a TRY 1,000 investment
Assume you start with TRY 1,000, one dollar costs TRY 20, and an asset costs $100. First convert the budget: 1,000 / 20 = $50. Then calculate the quantity purchased: 50 / 100 = 0.5 units. That quantity remains constant in this example because there are no distributions, splits or additional purchases. A currency movement does not itself increase the number of units held. It changes the value assigned to those units in the reporting currency.
At the end, suppose the asset costs $120 and one dollar costs TRY 25. The holding is worth 0.5 × 120 = $60. Converting it gives 60 × 25 = TRY 1,500. Compared with the initial TRY 1,000, that is a TRY 500 gross increase and a 50% nominal return. In dollars, the holding increased from $50 to $60, a 20% return. Both statements are consistent because their starting and ending values use different currencies.
| Step | Calculation | Result |
|---|---|---|
| Convert starting budget | 1,000 / 20 | $50 |
| Purchase quantity | 50 / 100 | 0.5 units |
| Value in dollars | 0.5 × 120 | $60 |
| Value in lira | 60 × 25 | TRY 1,500 |
Multiply return factors rather than adding rates
The asset rose 20%, and the lira price of a dollar rose 25%. Adding those percentages produces 45%, not the correct 50%. The additional dollar value generated by the asset is also translated at the ending exchange rate. With matching dates, the combined return is (1 + asset return) × (1 + FX change) − 1. Here, 1.20 × 1.25 − 1 = 0.50. The extra five percentage points come from the interaction term, 0.20 × 0.25.
Currency can also erase a gain. If the asset rises 20% while the lira price of a dollar falls 20%, the result is 1.20 × 0.80 − 1, or minus 4%. If the asset falls 20% while the dollar's lira price rises 25%, the result is 0.80 × 1.25 − 1, or zero. In that second case the investor has recovered the nominal lira contribution but lost dollar value. Neither case suggests that currency exposure removes investment risk.
Check which way the exchange rate is quoted
Every rate here answers “how many lira buy one dollar?” Moving from 20 to 25 is a 25% increase in that quote. The inverse quotes are 1 / 20 and 1 / 25 dollars per lira, a 20% decrease. Those changes are not contradictory. Percentage changes in reciprocal prices are not obtained by simply reversing the sign. Write the base and quote currencies above a spreadsheet column before using its numbers in a formula.
Dates matter alongside quote direction. An asset's close and an exchange-rate observation from another day describe a different combination. Weekends and market holidays require a stated missing-day convention. Silently borrowing a future observation can insert information unavailable on the purchase date. If a tool uses monthly representative rates, treat that as a monthly approximation rather than assuming it reproduces the precise conversion available for every daily transaction.
DCA needs a conversion for each contribution
Consider two TRY 1,000 contributions. At rates of 20 and 25 lira per dollar, they purchase $50 and $40 respectively. Keep the asset price at $100 for both purchases, giving 0.9 units in total. If the final asset price is still $100 and the ending rate is 30, the value becomes 0.9 × 100 × 30 = TRY 2,700. Contributions total TRY 2,000. The asset price did not change, but the reporting-currency value did.
Averaging the two rates to 22.5 and dividing TRY 2,000 by that number produces $88.89, not the $90 actually acquired. Dividing by an average is not equivalent to adding the separate conversions. If asset prices also vary, another source of difference appears. A reproducible DCA ledger therefore pairs contribution date, amount, asset price and exchange rate on each row. A single starting-date exchange rate cannot reconstruct money invested much later.
A reference rate is not an executable quote
The European Central Bank describes its reference exchange rates as informational and discourages their use for transaction purposes. Such a rate can be a traceable input without proving that your bank offered it. Dealing spreads, fees and transaction times can change a real outcome. Our single-rate examples deliberately exclude these effects. To reconcile an account statement, separate the original currency purchase from the eventual conversion back rather than assuming identical frictionless dealing conditions.
A fund's trading currency also does not establish its underlying currency exposure. A fund bought in euros may hold assets denominated elsewhere. A currency-hedged share class follows a separate policy. Selecting EUR as a calculator's reporting currency does not create that hedge. Determine hedging treatment from the product documentation, not from the currency symbol next to its market price. Reporting and risk management are different operations even when both involve exchange rates.
Choose the comparison that matches the question
If the future expense is in lira, a TRY result is useful, but inflation still matters for purchasing power. If the expense is in dollars, looking only at nominal lira growth can misstate progress toward it. Save the outcome in both currencies and identify which one matches the spending goal. This does not decide whether an investment is suitable; it makes the measurement explicit instead of letting the most flattering number choose the narrative.
When using the investment calculator, keep the asset and dates fixed while examining currency effects. Entering 1,000 in both runs, however, means investing TRY 1,000 in one case and $1,000 in the other. Those are not equal budgets. Convert the initial amount at the initial rate if you want the same economic investment. Read the displayed data dates and methodology. A larger numeral in another currency is not an additional gain.
