What is compound interest?

Compound interest is interest on the initial principal plus interest already earned, which makes savings grow faster than simple interest.

Can I add one-off contributions?

Yes. Use the irregular contribution schedule to add additional amounts at specific periods. The calculator includes them in the growth simulation.

Can I change the interest rate later?

Yes. Use the variable rate schedule to set a new annual rate starting from any period. The new rate applies from that period onwards.

Is the chart accurate?

The chart is generated from the same period-by-period simulation used for the numeric results, so it reflects the same balances for your inputs.

Compound Interest Calculator — Calculate Savings Growth

Calculate Compound Interest & Growth (with chart & schedules)

Initial principal (amount)

Annual interest rate (%)

Period (years)

Compounds per year

Periodic contribution

Amount added each contribution period (if using uniform contributions).

Contribution frequency

Contribution timing

Advanced: Custom schedules

Add irregular contributions or change interest rate over time by specifying period numbers (1 = first compound period).

Irregular contribution — period #

Amount

Variable rate — start period

Annual rate (%)

Schedules are optional. If schedules exist, they override uniform contributions or fixed rate for the specified periods.

Calculations run locally in your browser. Use schedules for irregular inputs or changing rates; export CSV to chart elsewhere.

Future value

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Total contributions

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Interest earned

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Effective annual yield (approx)

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Growth chart

Interactive chart shows balance over each period. Hover to see values. Use Export CSV for full data.

How to Use

Enter starting amount

Set your initial principal (the amount you have now).

Set rate & compounding

Choose the annual interest rate and compounding frequency (monthly is common).

Add schedules (optional)

Use irregular contributions or variable rates for advanced scenarios; otherwise leave them empty.

Why use this Compound Interest Calculator?

Visualize growth: See how small regular or irregular contributions build wealth with compounding.
Test scenarios: Try changing rates mid-way or one-off contributions to model real-life changes.
Export & analyze: Download CSV and open in Sheets/Excel for detailed charts or reports.
Privacy-first: All computation runs in your browser — no uploads.

Frequently Asked Questions (FAQs)

Compound interest is interest on the initial principal plus interest already earned — it increases growth over time.

Yes — use Advanced → Irregular contribution to add a one-off amount at any period number. The simulation will include it.

Yes — add Variable rate entries in Advanced → Variable rate. Specify the starting period and new annual rate; the new rate applies from that period onward.

The chart is a period-by-period visualization produced from the same simulation used for the numbers. It's client-side and interactive.