Entry — Compound Growth
Calculate how your money can grow with compound interest over time. See your total interest, contributions, and projected balance with different compounding options.
Starting amount can’t be negative.
Enter a rate between 0% and 30%.
See the Inflation Calculator for a dedicated purchasing-power tool.
- Initial principal$0
- Total contributions$0
- Interest earned$0
- Investment period0
- Annual interest rate0.00%
- Compound frequencyMonthly
- Effective annual rate0.00%
| Year | Starting Balance | Contributions | Interest | Ending Balance |
|---|
Explore The Options
Compare Compounding Frequency
Using your current amount, rate, and period, here’s how the final balance changes with each compounding frequency. The difference is often small at modest rates, but it can grow more meaningful over longer periods or higher rates.
| Frequency | Future Value | Effective Annual Rate |
|---|
The Math
Compound Interest Formula
For a lump sum with no recurring contributions, compound growth follows one formula. Once regular contributions are added, each deposit compounds for a different length of time — so the calculator simulates the balance period by period instead.
- Principal — your starting amount.
- r — annual interest rate, as a decimal.
- n — compounding periods per year.
- t — time, in years.
Worked Example
Compound Interest Example
- Starting amount
- $10,000
- Annual rate
- 5.00%, monthly compounding
- Period
- 10 years
- Interest earned
- ≈ $6,470
- Final balance
- ≈ $16,470
With no contributions, $10,000 at 5% compounded monthly for 10 years grows to about $16,470 — interest alone accounts for roughly $6,470 of that.
- With $300/month added
- Total contributions
- $36,000
- Final balance
- ≈ $57,000
Adding a $300 monthly contribution to the same scenario raises the projected final balance to roughly $57,000 — contributions and interest are now both meaningful parts of the total.
Understanding The Basics
What Is Compound Interest?
- 01
Interest earns additional interest
Once interest is added to your balance, future interest is calculated on that larger amount too.
- 02
Time can significantly affect growth
The longer money compounds, the larger the base it’s growing from — and the more that growth accelerates.
- 03
Higher rates generally increase growth
A higher annual rate compounds faster, though it may come with more risk or different terms.
- 04
Compounding frequency matters, a little
More frequent compounding (daily vs annually) modestly increases the final balance at the same nominal rate.
- 05
Regular contributions accelerate growth
Adding money on a schedule builds a meaningfully larger balance than a single lump sum alone.
- 06
Returns are never guaranteed
This calculator projects an assumed constant rate — real accounts and markets vary.
A Key Distinction
Compound Interest vs Simple Interest
Simple interest is calculated only on the original principal for the entire period. Compound interest is recalculated on the growing balance, so earlier interest starts earning interest of its own.
On $10,000 at 5% for 10 years: simple interest earns a flat $5,000 (10 × 5% × $10,000). Compound interest, compounded annually, earns roughly $6,289 over the same period — the gap widens further with more frequent compounding or longer periods. Try the Simple Interest Calculator for a side-by-side comparison.
“Simple interest pays you on what you put in. Compound interest pays you on what you put in — and on what it’s already earned.”
A Common Mix-Up
Nominal Rate vs Effective Rate
These two numbers can look similar but describe different things — knowing which one you’re looking at matters when comparing accounts.
- 01
Nominal annual rate
The stated yearly rate before accounting for how often it compounds.
- 02
Effective annual rate
The actual annual growth rate once compounding frequency is factored in — always equal to or higher than the nominal rate.
- 03
Compounding frequency
More frequent compounding pushes the effective rate further above the nominal rate.
A 5% nominal rate compounded monthly has an effective annual rate of about 5.12% — small on paper, but it’s the number that actually reflects your yearly growth.
Transparency
Compound Interest Calculator Assumptions
- 01
Interest rates may not remain constant
This calculator assumes one fixed rate for the entire period.
- 02
Actual returns may vary
Real investment or account performance can differ meaningfully from a projection.
- 03
Fees and taxes aren’t included
These can reduce real-world results unless factored into your assumed rate.
- 04
Contributions may occur at different times
Real deposits can be missed, delayed, or adjusted compared to a fixed schedule.
- 05
Inflation can reduce purchasing power
A growing balance doesn’t guarantee growing purchasing power.
- 06
This is a projection, not a guarantee
Actual results will differ from any estimate shown here.
Questions
Frequently Asked Questions
See what compounding could do for your own numbers.
Free, fast, and no account required — run the calculator above with your own amount and rate.