A 4% interest rate means something very different when inflation is 1% than when it is 6%. The real rate strips inflation out: it is what a lender earns, or a borrower pays, after prices have risen.
FinVolio uses each central bank's preferred underlying measure: the trimmed mean for the RBA and core PCE for the Fed.
Why it matters
Economists compare the real rate with a neutral rate, the level that neither speeds nor slows the economy. Estimates of neutral are uncertain, but a real rate well above zero is usually read as restrictive and one below zero as stimulatory.
See the data: RBA cash rate, Trimmed mean.
General information, not advice.