Interest Rate Differential Calculator

A positive differential means the currency you're holding pays a higher interest rate than the one you're funding the position with, this is the foundation of a carry trade, potentially earning you the difference as an ongoing return, in addition to any price appreciation.

Not automatically, currency price movements can easily overwhelm the interest differential, particularly during periods of volatility or risk-off sentiment, when carry trades are typically unwound quickly. The differential is one input, not a standalone trading signal.

Your broker's swap rate for holding a position overnight is directly derived from the interest rate differential between the two currencies, adjusted for the broker's own markup. A positive differential in your favour often (though not always) means you receive a swap credit rather than paying a fee.

Use each country's current central bank policy rate, for South Africa, the SARB repo rate, for other countries, their equivalent benchmark rate. These rates change periodically following central bank decisions, so verify you're using the current figure.

Yes, whenever either country's central bank changes its policy rate, the differential shifts immediately, worth checking current rates periodically rather than assuming a figure calculated weeks or months ago still applies.

Not automatically, a large differential can also signal one currency is under significant stress or facing high inflation, both of which can be reflected in its elevated interest rate, worth considering the broader context, not just the number itself.

Your broker's swap rate is derived from this underlying interest rate differential, adjusted for their own markup and specific calculation method, this calculator gives you the theoretical base figure your actual swap rate is built from.

No, some major currency pairs currently have relatively similar rates between the two countries, producing a small or negligible differential, carry trade strategies tend to focus on pairs with genuinely wide, persistent differentials.

Yes, if the base currency's central bank cuts rates while the quote currency's stays steady or rises, a previously positive differential can turn negative, meaning a position that once earned carry could start costing it instead.