Compound Interest Calculator

What Compound Interest Calculator helps you do

Project how an initial balance grows with recurring contributions and compound frequency, then compare illustrative return scenarios side by side. Useful for savings goals and education — not a market forecast. The output separates what you put in from what the assumed rate adds, which is often the more useful number.

All math runs locally in your browser. Haivix does not fetch market returns or store inputs.

How it works

Each month the balance grows by the effective monthly rate implied by your annual rate and compound frequency: (1 + r/n)^(n/12) - 1. Contributions are added before or after that growth depending on the timing setting. The scenario table runs the same inputs at 6%, 8% and 10% so the assumptions can be compared.

How to use Compound Interest Calculator

1. Enter starting balance, contribution amount, frequency, and compounding interval.
2. Set the duration, rate, timing and currency.
3. Review projected balances and compare the scenario rates.
4. Change one input at a time if you want to isolate its effect.

When to use it

• Model monthly savings toward a target date with different assumed returns.
• Separate principal and growth when explaining compounding to stakeholders.
• Compare contribution timing (beginning vs end of period) on long horizons.
• Test how a higher contribution changes the end balance.
• Show the effect of compounding frequency on the same rate.
• Plan a savings goal without implying a market forecast.

When not to use it

• Do not treat the 6/8/10% scenarios as a forecast or investment advice.
• Do not use it for tax, fee or inflation modeling.
• Do not model irregular contributions or withdrawals.

Example

A 10,000 starting balance with 200 a month for ten years at 8% compounded monthly ends well above the sum of the deposits. The table shows the same plan at 6% and 10%, and the contribution total makes clear how much of the balance is money saved rather than money earned.

What you can do with Compound Interest Calculator

• Enter a starting balance and an annual rate.
• Add recurring contributions at a chosen frequency.
• Choose the compounding frequency and contribution timing.
• Compare 6%, 8% and 10% return scenarios.
• See a growth chart and a side-by-side table.
• Switch the display currency.
• Change the currency without changing the math.

Example: model a monthly savings plan

Enter the starting balance, a monthly contribution and a duration in years. Choose how often the interest compounds and whether contributions go in at the beginning or end of each period.

Compare the scenario table rather than treating one rate as a prediction. The gap between 6% and 10% over ten years is the point of the comparison, not a promise.

Check the chart against the table and use the contribution total to see how much of the final balance came from deposits rather than growth.

What to know before you start

• Assumed rates are hypothetical; actual investment returns vary and are not guaranteed.
• Taxes, fees, inflation and withdrawals are not modeled.
• Contributions are assumed to be regular, not irregular.
• The comparison rates are illustrative, not a market forecast.
• The result is arithmetic, not financial advice.

Common mistakes

• Reading the scenario table as a guaranteed return.
• Ignoring the contribution total when judging the final balance.
• Mixing an annual rate with a monthly contribution frequency incorrectly.
• Assuming beginning-of-period contributions make a large difference on a short horizon.
• Forgetting that inflation and fees are not modeled.
• Changing the contribution frequency without changing the amount to match.

Troubleshooting

If the result seems low, check the duration and whether the rate is annual, not monthly.

If the balance barely grows, the compound frequency or the rate may be set to zero.

If beginning and end timing look identical, the difference is small for a short duration; extend the years to see it.

If the currency symbol is wrong, change the selector; no conversion is applied.

If you need a monthly rate, divide the annual rate by 12 only when the tool's compounding setting matches that assumption.

If the scenario table and the chart disagree, check that the same currency and inputs apply to all three rates; the scenarios share the same contribution plan.

If the duration is entered in months, convert it to years before calculating.

If the final balance is lower than the deposits, the rate is zero or the duration is too short; negative growth is not modeled.

Related standards and documentation

• Compound interest is a mathematical formula; the assumed rate is an input, not a standard value.
• APR and APY conventions differ in how they express the same rate.