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Nominal Interest, APY & Deposit Growth Calculator

Convert a nominal annual rate to a compounded annual yield and estimate a deposit balance over a chosen term.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Results are estimates for planning and education. Confirm rates, taxes, fees, and legal requirements with the relevant institution or a qualified professional before making a financial decision.

Formula and method

At a 10% nominal rate compounded yearly, the modeled annual yield is 10%. A 1,000 deposit grows to 1,100 over 12 months with no additional cash flows.

Annual yield = (1 + r/n)^n − 1; final balance = initial balance × (1 + r/n)^(n × years)

Worked example

Enter these known values and leave the other values blank.

Initial deposit
1000 USD
Nominal annual interest rate
10 %
Compounding periods
Yearly
Deposit term
12 mos
Modeled annual percentage yield
10 %
Modeled final balance
1100 USD

Assumptions and limitations

  • Assumes a constant nominal rate, reinvested interest and no deposits, withdrawals, fees or taxes. The term must be positive and the periodic growth factor must exceed zero.
  • Weekly and daily options use 52.1775 and 365.242 periods per year in this model. These average-year conventions are not a dated account accrual schedule; match the product’s actual compounding terms before comparing it.
  • This is a mathematical annual yield. A regulated account disclosure can depend on product-specific terms and conventions beyond this formula.

Common questions

Why can APY exceed the nominal rate?

With a positive rate and more than one compounding period per year, later interest also earns interest. The nominal rate alone does not include this effect.

How do I enter a one-year term?

The default term unit is months, so enter 12. Alternatively, switch the term unit to years and enter 1.

References

Bookify adds explicit model-domain checks: The periodic growth factor must be positive. The modeled annual yield must exceed minus 100 percent.

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