Compound Interest Calculator (USD)
Project your compound growth in one aligned summary
Quick compound interest FAQs
What does this calculator show?
It shows your projected future value in USD, total contributions, total interest earned, and effective APY based on your inputs.
How often are contributions applied?
We treat the regular contribution as paid at the end of each compounding period (for example monthly if you picked 12×).
Can I use it for both savings and investments?
Yes. Use a realistic long-run rate for your product. It’s a projection, not a guarantee.
Does it include inflation, taxes, or fees?
No. It keeps the math clean. Adjust for those factors separately in your own planning.
How to read your compound interest summary
1. One summary for your whole plan
This calculator mirrors your other finance tools on the site: one aligned card that answers “What will my savings be worth if I stick to this plan?”. Instead of juggling multiple boxes, you get future value, contributions, interest earned, and compounding details in a single snapshot that works on mobile and desktop.
2. Start with realistic inputs
Pick an annual rate that matches your account: low single digits for cash, more conservative for long-term investing than headline returns. Choose the compounding schedule stated by your bank or broker. Use years, not months, to keep the horizon intuitive. If you’re not sure, try a range (e.g., 4%, 6%, 8%) and compare where your future value lands.
3. Use contributions to model real behavior
The regular contribution is where compounding becomes tangible. A fixed amount every period, even if small, stacks over hundreds of periods. Because the contribution is applied at the end of each compounding period, the output is slightly conservative versus “perfectly early” deposits. If you pay yourself first at the start of the month, the real outcome is a bit better than shown.
4. Read the breakdown, not just the big number
The summary separates what you put in from what growth delivered. Seeing total contributions next to total interest helps you judge whether the plan is doing enough, and avoids the trap of assuming every big future number is “free money”. If most of the final balance is contributions, consider raising the rate target carefully or extending the time horizon instead of chasing unrealistic returns.
5. Compare scenarios quickly
Because the layout is simple, it’s easy to duplicate scenarios: bump the contribution, adjust the years, or tweak the APR and re-run. Keep the compounding setting consistent when comparing options so differences reflect the levers you’re actually changing, not a hidden math switch.
6. Treat results as a planning compass
Real-world returns move around. Use this tool as a compass, not a promise: check periodically whether your actual balance is above or below the projected path, then adjust deposits, risk, or timing with eyes open.
Formula snapshot
1. Let P be your initial amount, C your contribution per compounding period, r the rate per period, and n the total number of periods.
2. Periodic rate: r = (APR ÷ 100) ÷ m, where m is compounding periods per year.
3. Future value with end-of-period contributions:
FV = P·(1 + r)n + C · (( (1 + r)n − 1 ) ÷ r) (if r > 0)
If r = 0: FV = P + C·n.
4. Total contributions = C·n. Total interest = FV − P − contributions.
5. Effective APY = (1 + r)m − 1 for your chosen m.