Direct answer
Interest rates in forex refer to how differences in borrowing costs between countries affect currency values. In practice, forex prices react to (1) expectations about future interest rates, (2) expected inflation and economic growth that determine real returns, and (3) how investors compare the risk and convenience of holding one currency versus another.
Explanation: the main mechanisms
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Relative yields and expected returns Currencies are affected by the interest income (or cost) investors expect to earn or pay. When market participants expect one country’s interest rates to be higher for longer than another’s, that currency can become relatively more attractive—because the expected return from holding assets priced in that currency changes.
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Central-bank expectations vs. current announcements Forex often moves around changes in expectations rather than only the latest official decision. The relevant input is what investors believe will happen to future policy rates, not just what was announced today.
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Real interest rates and inflation expectations Nominal interest rates are not the whole story. If higher nominal rates mainly reflect higher expected inflation, the real return may not be as attractive. So exchange rates can respond to changes in inflation forecasts as well as policy rates.
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Funding, risk pricing, and carry trade behavior (conceptually) Large interest-rate gaps can encourage investors to fund in a lower-rate currency and hold assets in a higher-rate currency. However, this is not a one-way effect: forex value changes can offset interest differences, and risk conditions can alter how investors price volatility and credit.
Example checks (how to verify the relationship without predicting outcomes)
- Compare rate expectations rather than only one rate figure: look at whether the market view of future policy changes has shifted.
- Check the inflation and growth context: if higher rates coincide with rising inflation expectations, real-yield effects may differ.
- Consider the risk backdrop: during stress, currencies can move for reasons unrelated to rates, such as safe-haven preferences.
- Use both currency pairs you compare: the effect is usually about the rate difference between two countries.
Limitations and uncertainty
- Interest rates do not determine forex on their own; exchange rates reflect many inputs at the same time.
- Reactions can be short-lived because expectations can reverse quickly.
- The direction and size of the impact depend on whether the market already priced in the information.
- No outcome can be guaranteed, and past patterns do not ensure future results.