Compound Interest Calculator
See how fast your savings can grow. Get future value, total contributions, and total interest, then adjust your monthly deposit until the plan feels realistic.
Show yearly breakdown
| Year | End balance | Contributions | Interest |
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Educational estimates only. Results depend on real-world rates, timing of deposits, fees, and taxes.
Last updated: May 9, 2026
Compound interest calculator (what people really search for)
Most people land on a compound interest page with one of three questions: How much will I have? How much should I invest each month? Or how much of my result is interest vs. my own deposits? This page answers all three with clear outputs and a yearly breakdown you can sanity‑check.
What is compound interest?
Compound interest means you earn interest on your original deposit (the principal) and on interest that’s already been added. Over time, your balance can grow faster because the “interest earns interest.” The longer the timeline, the more visible the compounding curve becomes.
How to use this calculator to hit a savings goal
If you have a target, like $25,000 in 5 years or $100,000 in 10 years, set your years and a realistic rate, then adjust your monthly contribution until the future value meets your goal. This turns the tool into a practical “how much should I save per month?” calculator.
If you’re not sure about the rate, start conservative. A plan that works with cautious assumptions is easier to stick to, and sticking to it is what makes the math real.
Formula (and why the real world is messier)
A common base formula for compounding is:
A = P(1 + r/n)^(n·t)
- A = amount after time t
- P = principal (initial deposit)
- r = annual rate (decimal)
- n = compounding periods per year
- t = years
When you add monthly contributions, the exact outcome depends on timing (beginning vs. end of month) and real‑world details like rate changes, fees, and taxes. We model monthly contributions and apply compounding frequency to give an estimate that’s easy to understand and compare.
Example (the one people Google)
A classic scenario is $1,000 + $100/month at 7% for 10 years. The outputs are designed to match common search intent:
- Future value shows where you could end up.
- Total contributions shows what you actually put in.
- Total interest shows the growth on top of your deposits.
A good rule of thumb: if your total interest is still small early on, that’s normal. Compounding often looks quiet at first, then noticeably faster later. That’s why the timeline matters so much.
APR vs. APY (which number should you enter?)
Savings accounts often advertise APY (effective annual yield after compounding). Loans usually show APR (annual percentage rate). For savings/investing projections, APY‑like numbers are typically more comparable. If you only have APR, you can still use it for scenario planning.
Compounding frequency: does daily vs. monthly matter?
It matters, but less than most people expect. Daily compounding can produce a slightly higher result than monthly compounding at the same stated annual rate. The bigger levers are your rate, your monthly contribution, and your timeline.
What to do if your result looks too optimistic
- Use a conservative rate for investing scenarios.
- Reduce the rate to account for fees and taxes (for example, subtract 0.5%-1%).
- Extend the timeline, time is usually the most underrated input.
FAQ
How much will $10,000 be worth in 10 years?
Enter $10,000 as the initial deposit, set monthly contribution to $0, pick a rate and compounding, then set years to 10. The future value is your estimate.
How much should I invest each month to reach my goal?
Set your years and rate, then increase the monthly contribution until the future value matches your target (or slightly exceeds it).
What interest rate should I use?
For savings, use the account APY. For investing, use a conservative long‑term assumption and treat the result as a scenario, not a promise.
Is this APY or APR?
It accepts an annual rate. Use APY for savings/investing estimates when available; APR is fine for planning scenarios.
Does compounding daily make a big difference?
Usually it’s a small difference compared to rate, monthly contribution, and years invested. Those inputs dominate the outcome.
