Money Tools

APY Calculator

Convert a nominal interest rate into APY and estimate one-year growth from a starting balance.

Updated April 11, 2026
Free online tool
Planning and research use

Why this page exists

A quoted interest rate does not always tell the full story, because compounding changes what the balance really earns over a year. This calculator converts a nominal annual rate into annual percentage yield and, when a starting balance is entered, shows what that rate could look like after one year.

Interactive tool

Run the estimate

Enter your numbers and read the result first, then use the sections below to understand what affects the outcome.

Calculator

APY calculator

Convert a nominal annual interest rate into annual percentage yield based on compounding frequency.

Result

4.59%

Estimated APY from the nominal rate and compounding frequency entered, with a one-year balance projection from the starting balance.

Annual percentage yield4.59%

Ending balance after one year$10,459.40

Interest earned after one year$459.40

Compounding periods per year12

A nominal rate of 4.50% compounded monthly produces about 4.59% in APY.
With a starting balance of $10,000.00, that yield would grow the balance to about $10,459.40 in one year.
More frequent compounding pushes APY slightly above the nominal rate because interest starts earning interest during the year.

This is a planning estimate. Banks and investment products may use different assumptions, fees, or timing details that change the real yield.

Planning note

Last updated April 11, 2026. Use this tool to compare scenarios and plan ahead, then confirm important details with the lender, employer, insurer, contractor, or other qualified provider involved in the final decision.

How it works

What the calculator is doing

Enter the nominal annual rate and choose how often interest compounds.

The calculator converts that rate into APY using standard compounding math.

If you add a starting balance, it also estimates the ending balance and interest earned after one year.

Understanding your result

APY is often the better comparison number when savings products use different compounding schedules. Two accounts can advertise similar nominal rates while the one with more frequent compounding edges ahead over time.

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Examples

Ways people use this tool

Example scenarios help turn a quick estimate into a more useful comparison or planning step.

Compare savings account offers

Use the same nominal rate with different compounding schedules to see whether the yield changes in a meaningful way.

Project one-year interest

Add a starting balance to turn the yield into a dollar estimate for the next 12 months.

Understand APY vs APR wording

Run the calculator to see why APY usually ends up slightly above the nominal rate when interest compounds during the year.

FAQ

Common questions

What is the difference between a nominal rate and APY?

The nominal rate is the stated annual rate before compounding is accounted for. APY adjusts for compounding so it shows what the balance may actually earn over a full year.

Why does compounding frequency matter?

More frequent compounding means interest starts earning interest sooner, which pushes APY slightly higher than the nominal rate.

Does this include taxes or fees?

No. This calculator focuses on the yield math only, so taxes, account fees, and balance rules can change the real return.

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Money ToolsUpdated April 11, 2026