Is this the inverse of the APR converter?

Yes, when both tools use the same constant rate and number of equal compounding periods — entering the resulting APY back into the APR converter with the same period count returns the original nominal rate, as the automated tests confirm.

Does compounding more often always help meaningfully?

The APY keeps rising with frequency, but with diminishing returns — the jump from annual to monthly compounding is much larger than from daily to hourly at the same nominal rate, since the formula approaches a continuous-compounding limit.

Does this account for fees, tiers or promotional rates?

No. It is a pure compounding-frequency conversion of one constant rate; it does not include account fees, balance tiers, promotional periods, or any other terms that a real deposit account's advertised APY might already bundle in.

APY Calculator

Convert a nominal interest rate into its effective annual yield (APY).

This tool runs entirely in your browser. Your files are never uploaded to a server.

Nominal annual rate (%)Compounding periods per year

6.168%

Effective annual rate (APY)

What this calculator does

Converts a nominal annual interest rate into its effective annual percentage yield (APY) for a chosen number of equal compounding periods per year — the actual annual return once compounding within the year is accounted for.

How to use it

Enter the nominal annual rate and an integer compounding frequency from 1 to 366, such as 12 for monthly or 365 for daily. Compare the result only against rates disclosed with the same compounding assumption.

Worked example

A 6% nominal annual rate compounded monthly (12 periods) converts to an APY of about 6.167781%. Entering that APY back into the related APR converter with 12 periods returns approximately 6% nominal, and automated tests verify this round trip.

Formula and precision

For nominal decimal rate r and n compounding periods, APY = (1 + r/n)^n − 1. The implementation uses logarithm and exponential functions that stay accurate for small rates, keeps full floating-point precision internally, and rounds only the displayed percentage to three decimals.

Why APY rises with more frequent compounding

Each compounding period adds interest on interest already credited. At the same nominal rate, more frequent compounding produces a slightly higher APY — daily compounding yields more than monthly, which yields more than annual — though the gap shrinks as frequency increases further.

Assumptions and limits

The formula assumes one constant periodic rate, equal compounding intervals, full reinvestment of interest, and no deposits or withdrawals during the year. It does not model tiered or promotional rates, changing balances, fees, day-count conventions, or an institution's specific rounding rules.

Regional terminology

APY, effective annual rate (EAR) and similar disclosed yields are not labeled identically everywhere, and some jurisdictions apply different calculation conventions (actual days, minimum-balance rules) to advertised rates. Treat this as a compounding-only mathematical conversion, not a specific bank's or country's regulated disclosure.

Sources, warning and privacy

The compounding formula and terminology were checked against U.S. Truth in Savings Act guidance (Regulation DD) published by the Consumer Financial Protection Bureau. Reviewed September 2026. This educational converter is not financial or investment advice. It runs locally in the browser; Quiklio does not upload entered rates.

Frequently Asked Questions

Is this the inverse of the APR converter?: Yes, when both tools use the same constant rate and number of equal compounding periods — entering the resulting APY back into the APR converter with the same period count returns the original nominal rate, as the automated tests confirm.
Does compounding more often always help meaningfully?: The APY keeps rising with frequency, but with diminishing returns — the jump from annual to monthly compounding is much larger than from daily to hourly at the same nominal rate, since the formula approaches a continuous-compounding limit.
Does this account for fees, tiers or promotional rates?: No. It is a pure compounding-frequency conversion of one constant rate; it does not include account fees, balance tiers, promotional periods, or any other terms that a real deposit account's advertised APY might already bundle in.

APR Calculator

Convert APY into an equivalent nominal annual rate; this is not a fee-inclusive loan APR.

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