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Deposit Interest Models

Compare simple maturity growth, nominal compounding, and periodic equivalent-rate payouts.

  • 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

A 1,000 deposit at a 10% nominal annual rate, compounded annually for two years, matures at 1,210 with 210 of interest.

Simple maturity = P(1+rt); compound maturity = P(1+r/m)^(mt). The separate payout model uses the effective annual rate.

Worked example

Enter these known values and leave the other values blank.

Principal amount
1000 USD
Interest rate
10 %
Term
2 yrs
Compounding frequency
Annually
Maturity amount
1210 USD
Total interest
210 USD
Payout per interest period
100 USD
Total payout
200 USD

Assumptions and limitations

  • The cumulative maturity uses a nominal annual rate. The non-reinvested payout branch treats the entered rate as an effective annual rate; these are separate scenarios.
  • The simple payout field divides total term interest by frequency only, so it is a per-term share rather than a true monthly amount unless term is one year.
  • Use one currency throughout. Retained currency selector factors are a historical snapshot, not live exchange rates.
  • Clear an editable unknown before solving an inverse. Selection controls and forced outputs cannot be inferred.

Common questions

What does this model assume?

The cumulative maturity uses a nominal annual rate. The non-reinvested payout branch treats the entered rate as an effective annual rate; these are separate scenarios.

Can I use the currency menu as a current quote?

No. Keep amounts in one currency; conversion factors are a captured historical snapshot.

References

Required model inputs: Principal must be positive. The deposit term must be positive. Use a positive deposit rate; zero-rate inverses are outside this model.

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