Compare a quoted nominal savings rate with its effective yearly yield, or reverse the calculation to find the nominal rate behind an APY. The projection also shows how regular deposits change your ending balance.
How to use this calculator
Choose APR to APY when you have a nominal interest rate, or APY to APR when you have an advertised annual yield. Select the account's compounding frequency, enter the initial deposit, and set a term of at least one month. Under Regular deposits, choose an amount, frequency, and beginning or end timing.
Use Interest earned only for a fixed principal without intervening deposits or withdrawals. Enter actual interest and the whole number of days in the term.
Understanding the result
APY is an annual rate, even when your projection lasts less than one year. The ending balance includes your starting money, additional deposits, and interest. The schedule separates these components so deposits are not mistaken for investment gains. A display currency changes the labels; it does not convert exchange rates.
Examples
5% nominal interest, compounded monthly
A $10,000 deposit at a nominal rate of 5%, compounded monthly for one year, earns about $511.62 with no additional deposits. APY is 5.1162%, and the ending balance is $10,511.62.
Reverse a 5% APY
An account paying 5% APY with monthly compounding has a nominal annual rate of approximately 4.8889%. Entering 5% as the nominal rate instead would overstate the yield.
Formula
With nominal annual rate r as a decimal and n compounding periods per year:
APY = (1 + r/n)^n − 1
r = n × ((1 + APY)^(1/n) − 1)
Fixed-principal earned yield = (1 + interest/principal)^(365/days) − 1
For continuous compounding, APY = exp(r) − 1. Percent inputs are divided by 100 before applying the formulas.
Assumptions and limits
The projection keeps rates constant, reinvests interest, and excludes taxes and fees. Deposits use evenly spaced periods on a modeled year rather than a bank's actual posting calendar. Beginning-of-period deposits earn interest sooner. The interest-earned method uses a 365-day year; account disclosure conventions can differ for particular products and terms.
Formula reference
The CFPB's Regulation DD APY rules describe annualizing interest relative to principal and term. This tool is a planning estimate, not a bank disclosure generator.