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Interest rate converter

Convert between nominal, effective annual and continuously compounded interest rates.

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Interest rate converter
Paste one interest rate and this tool converts it into the other common forms: the nominal annual rate, the effective annual rate (also called APY), and the continuously compounded rate. It is built for the everyday confusion between a bank's advertised nominal rate and the effective rate you actually earn or pay once compounding is taken into account.
Start by telling the tool what your rate represents. A nominal rate needs a compounding frequency — daily, monthly, quarterly or annually — since a nominal rate on its own is meaningless without knowing how often it compounds. An effective annual rate or a continuously compounded rate need no frequency, because both already describe a full year's growth. The "convert to frequency" option controls which compounding frequency the headline nominal-rate result is expressed at, independent of the input's own frequency. Decimal places controls how many digits the result is rounded to, from whole percentages up to eight decimal places for precise financial work.
Turn on the comparison table to see the nominal and per-period rate at every common frequency plus continuous compounding side by side, so you can see at a glance how the same effective return looks whether it compounds daily or once a year. The periodic-rate option adds the single-period rate for the target frequency on its own line — the number a loan or savings schedule actually applies each period, as opposed to the annualized figure most rates are quoted in.
Everything runs locally in your browser; the rate you paste is never uploaded anywhere. Copy the result, download it as a .txt file, or send the output back into the input to compare a second rate.
FAQ
What is the difference between nominal and effective annual rate?
The nominal rate is the quoted annual rate before compounding is applied — for example "5% compounded monthly." The effective annual rate is what that actually grows to over a year once each compounding period's interest starts earning interest too, so it is always equal to or higher than the nominal rate.
What is a continuously compounded rate?
It is the theoretical limit of compounding infinitely often — the rate you would get if interest were added at every instant rather than daily or monthly. It is slightly lower than the nominal rate needed to reach the same effective annual rate at a finite frequency.
Why does the nominal rate change when I switch the target frequency?
A nominal rate only makes sense together with its compounding frequency. The tool holds the effective annual rate fixed and recalculates which nominal rate, at the frequency you choose, produces that same effective return — so a quarterly nominal rate will differ slightly from a monthly one even though both describe the same underlying growth.
Can I convert a negative rate, like a negative-yield bond?
Yes, as long as the resulting effective annual rate stays above -100%. A rate that would imply losing all your value or more is rejected with an explanation rather than producing a nonsensical result.
Is my rate uploaded anywhere?
No. The conversion runs entirely in your browser using JavaScript — nothing you type is sent to a server.