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Compound interest calculator

Project savings growth over time.

Project savings growth

Enter deposit, contribution, rate, and time to estimate a future balance.

$
$
%
years
%
Final balance $14,603.44
Total contributions $13,000.00
Interest earned $1,603.44
Estimated tax $0.00
After-tax balance $14,603.44

How to use this calculator

  1. 1

    Enter starting savings

    Add your current balance or planned deposit.

  2. 2

    Add contributions

    Enter the amount you expect to save each month.

  3. 3

    Set growth assumptions

    Choose interest rate, time period, and compounding.

  4. 4

    Review after tax

    Compare final balance, interest, and tax impact.

Formula

Compound growth: FV = P(1 + r/n)^(n x t)

With contributions: FV = principal growth + contribution growth

The page projects monthly deposits across the selected compounding schedule, then subtracts optional tax from interest earned.

Worked example

Saving $200 per month for five years:

Starting with $1,000 and adding $200 each month creates $13,000 in deposits. At 5% annual interest compounded monthly, the projected balance is about $14,603.44 before tax.

FAQ

How does compound interest work? +

Compound interest earns interest on both your original savings and previous interest. Over time, that reinvested interest can become a larger share of the balance.

What is the compound interest formula? +

The basic compound interest formula is FV = P(1 + r/n)^(nt). Contributions add another future-value term based on the same rate and time period.

How often should savings compound? +

Savings compound based on the account or investment rules. Monthly compounding grows slightly faster than quarterly or yearly compounding at the same annual rate.

Does this calculator include taxes? +

Yes, the optional tax rate applies to the interest earned, not to your original deposits. Leave tax at 0% if it does not apply.

Are monthly contributions added before interest? +

This calculator adds each monthly contribution before any compounding event in that month. Real accounts may use daily balances or different deposit timing.

About this calculator

This compound interest calculator projects how savings can grow from an initial deposit, monthly contributions, interest, compounding, and taxes. Use it to compare realistic saving habits before setting a target.

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Make the savings habit visible

Spendspace shows where money is going today, so you can protect the monthly contribution that makes compound growth possible.

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