Carry Trade Calculator

The carry trade calculator estimates profit or loss from the calculator’s simplified currency carry model. A carry trade typically involves borrowing or funding in a lower-yielding currency and investing in a higher-yielding one. The appeal is the interest-rate spread, but the danger is that exchange-rate moves can erase that spread. This tool combines the entered lending rate, borrowing rate, initial exchange rate, settlement exchange rate, days to settlement, and amount invested to produce a modeled return and dollar profit.

This page is informational, not investment advice; FX is high-risk. Carry trades are especially sensitive to leverage, volatility, funding liquidity, central-bank surprises, and sudden unwinds. The calculator helps explain the mechanics of its formula; it does not evaluate whether a trade is suitable, executable, or properly hedged.

Inputs and calculator behavior

Enter the initial exchange rate when the trade is opened and the settle exchange rate when it is closed. The calculator expects both exchange rates in the same quote direction. If the initial rate is price currency per base currency, the settlement rate must use that same convention. Next enter the annual lending rate earned on the higher-yielding currency and the annual borrowing rate paid on the funding currency. The form accepts percentages, so 0.75 means 0.75 percent. Finally, enter the number of days until settlement and the amount invested.

Invalid numbers, zero or negative exchange rates, negative days, and negative invested amounts. If the combined annual carry base cannot produce a valid exponent result, the result is invalid. The results include investment return, spot-rate differential, interest-rate spread, and amount invested.

Formula

The calculator first measures the exchange-rate move:

$\text{spot rate differential} = \frac{\text{settle exchange rate} - \text{initial exchange rate}}{\text{initial exchange rate}}$

It then calculates the annual interest-rate spread as a decimal:

$\text{rate spread} = \frac{\text{lending rate} - \text{borrowing rate}}{100}$

The calculation combines those values this way:

$\text{annual carry base} = 1 + \text{rate spread} \times (1 + \text{spot rate differential})$

The investment return and profit are:

$\text{investment return} = \text{annual carry base}^{\frac{\text{days}}{360}} - 1$

$\text{profit} = \text{amount invested} \times \text{investment return}$

This is a simplified model. It scales the interest spread by the exchange-rate differential; it does not directly translate the principal through the opening and closing exchange rates as a full cash-flow carry trade model would.

Worked example using the default inputs

The default values are an initial exchange rate of 0.85, a settlement exchange rate of 0.83, a lending rate of 0.75 percent, a borrowing rate of 0.50 percent, 180 days to settlement, and an invested amount of $1,000. The spot-rate differential is 0.83 minus 0.85, divided by 0.85. That equals -0.0235294118, or about -2.35 percent.

The interest-rate spread is 0.75 minus 0.50, divided by 100, which equals 0.0025. The annual carry base is one plus 0.0025 multiplied by one plus the spot-rate differential. Because one plus the differential is 0.9764705882, the annual carry base is 1.0024411765. The 180-day exponent is 180 divided by 360, or 0.5. Raising 1.0024411765 to the 0.5 power and subtracting one gives 0.0012198442. Multiplying by the $1,000 amount gives $1.2198442, displayed as about $1.22 profit.

This example is useful because the settlement exchange rate is lower than the initial exchange rate. Under this calculation, that adverse move reduces the spread-adjusted return but does not directly subtract a principal currency loss. That behavior is a compute-model limitation to remember when using the page for education.

How carry trades are used

Carry trades are used by macro funds, banks, and retail traders to express views on interest-rate differentials and currency stability. A trader may fund in a low-yielding currency and hold a higher-yielding currency, hoping the rate spread accrues while the exchange rate stays stable or moves favorably. Corporate treasurers may analyze carry when deciding whether to hold cash in one currency or hedge future flows, although business hedging usually has objectives beyond return maximization.

Use this calculator alongside related tools. The currency forward calculator shows how interest differentials affect a forward price. The interest rate parity calculator explains the no-arbitrage link between spot, forwards, and rates. The cross exchange rate calculator helps verify the spot quote direction before entering initial and settlement rates here.

Risks and tips

The classic carry risk is that a high-yielding currency weakens by more than the interest advantage earned. In stressed markets, carry trades can unwind together as investors reduce leverage, causing sharp currency moves and poor liquidity. Funding costs can also change. A central bank can raise the borrowing-currency rate or cut the lending-currency rate, compressing the spread that made the trade attractive.

For better analysis, write down the quote direction, separate interest carry from currency revaluation, and model transaction costs. If leverage is involved, test a much larger adverse exchange-rate move than seems likely; margin calls can force a position to close before a long-term view plays out. Treat the calculator result as a transparent formula output, not as a complete risk system.

Sources

• BIS, Triennial Central Bank Survey of foreign exchange and OTC derivatives markets — global FX market and derivatives background.
• Federal Reserve, Foreign Exchange Rates H.10 — reference exchange-rate publication for major currencies.
• European Central Bank, Euro foreign exchange reference rates — euro FX reference-rate context.