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Fundamental analysis

Interest rate differential

By Jarosław Wasiński • Published: • Updated:
The difference between comparable interest rates for two currencies or instruments, measured over the same tenor and basis. It helps explain forward pricing and some financing incentives, but is not a guaranteed currency return. Broker charges, exchange-rate changes, funding access and changing expectations also matter.
Example.

Comparable annual rates are 5% and 3%. The differential is 2 percentage points, or 200 basis points. This is not a promise of a 2% currency-pair return: FX moves, forward pricing, costs and funding conventions affect the outcome.

Comparable measurement bases

Use the same tenor, compounding convention and type of risk. Comparing an overnight rate with a ten-year yield mixes currency effects with maturity and premia.

Spot, forward and carry

Under explicit no-arbitrage assumptions, rate differences affect the relationship between forward and spot prices. Interest is not free profit independent of FX. Retail financing charges come from the provider's schedule and contract.

Repricing expectations

Markets respond to the expected future differential, not just today's value. A narrowing spread can matter even while it remains positive. Include inflation, credit risk, liquidity and possible cross-currency basis.

FAQ

Is the rate differential the broker's swap points?

No. It is an economic input; the actual credit or charge depends on the product and provider's terms.

Does a wider differential always strengthen the higher-rate currency?

No. Risk and changing expectations can outweigh it, and the difference may already be priced.

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Jarosław Wasiński

Editor-in-chief, ForexMechanics.com • Macro & FX analyst

Independent analyst and practitioner with over 20 years of experience in financial markets. Actively involved in Forex since 2007, with a focus on fundamental analysis, OTC market structure, and disciplined capital risk management.

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