Interest Rate Parity Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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The fastest way to make a finance estimate useful is to know exactly what went into it. Interest Rate Parity Calculator puts the relevant inputs beside the result so you can test the calculation instead of treating the number as a black box. On this page, it compares currency spot value with interest-rate-differential parity over the entered period.

What this calculator does

Interest Rate Parity Calculator compares currency spot value with interest-rate-differential parity over the entered period. Its visible inputs are Version, Number of days, Price currency annualized interest rate, Base currency annualized interest rate, Spot price. The article follows those fields and the calculation that is actually available on this page; it does not silently add live market feeds, tax tables, legal eligibility tests, or other variables that are not present in the tool.

How to use it

Enter Version, Number of days, Price currency annualized interest rate, Base currency annualized interest rate, Spot price. Use the units and percentage scale shown beside each field, and keep values on the same time basis when the formula compares income, rates, prices, balances, or work hours. Pay special attention to quote direction: reversing a currency quote changes the mathematics even when the same two currencies are involved.

How the calculation works

Covered parity uses spot × (1 + price-currency interest over the period) ÷ (1 + base-currency interest over the period). The uncovered option uses the page’s simplified spot adjustment based on the same period interest-rate differential.

Example

Using the page’s demonstration values (Version = covered; Number of days = 180; Price currency annualized interest rate = 5; Base currency annualized interest rate = 3) and leaving the remaining defaults unchanged, the calculator returns 1.110837 for covered parity forward price. Replace the sample inputs with values from the same period and definition before interpreting your own result.

How to interpret the result

Read the result as a model of the economic relationship represented by the inputs, not as a forecast of what an economy, market, currency, or policy authority will do next. Economic data are definition-sensitive: nominal versus real values, time periods, population bases, and price indexes must be aligned before comparing results.

Limitations and notes

The uncovered option is a simplified interest-differential estimate rather than a forecast of where the currency will actually trade. Simplified macroeconomic formulas hold other influences constant. Revisions to source data, measurement definitions, expectations, policy responses, market frictions, and nonlinear behavior can make real-world outcomes differ from the clean relationship shown here.