OmniCalcsCompound Interest Calculator
See how your money grows with compound interest, including monthly contributions.
How to Use This Compound Interest Calculator
Enter your starting balance, any monthly contribution, the annual rate and the number of years. Pick how often interest compounds (yearly, monthly or daily) and the calculator projects your final balance and how much of it came from interest.
- Initial principal โ the lump sum you start with.
- Monthly contribution โ added at the start of each month and then compounded.
- Compounding frequency โ more frequent compounding (daily over monthly) earns slightly more for the same nominal rate.
- Total contributed โ principal plus all contributions, so you can see pure interest growth.
Practical Example
Suppose you start with $5,000, contribute $200/month, and earn 7% compounded monthly for 20 years:
- Total contributed โ $53,000 ($5,000 + $200 ร 240)
- Future value โ $110,900
- Interest earned โ $57,900 โ more than the money you put in
Starting 5 years earlier would add roughly $45,000 to the final balance โ that's the power of time in compounding.
What Your Results Mean
- Future value โ what your money will be worth at the end, including growth.
- Total contributed โ the actual money you put in, for comparison.
- Interest earned โ the growth on top; the bigger this is relative to contributions, the more compounding helped.
Frequently Asked Questions
How does compounding frequency affect the result?
Interest credited more often earns interest on interest sooner. For the same nominal rate, daily compounding yields a slightly higher effective annual rate than monthly or yearly compounding.
What is the difference between nominal and effective rate?
The nominal rate is the stated annual rate. The effective rate accounts for how often it compounds. At 6% nominal, monthly compounding yields about 6.17% effective.
Why does the formula matter so much over time?
Compounding is exponential. Small differences in rate or contribution become large after 20-30 years, which is why starting early and contributing regularly matters.
Are monthly contributions added at the start or end of the month?
This calculator adds contributions at the start of each month, so they earn interest for that month. This slightly increases the balance compared to end-of-month contributions.
Is this result guaranteed?
No. Real investment returns fluctuate and may be lower or higher than the rate you enter. Use this as a planning estimate, not a guarantee.
Learn More
Read our in-depth guide: Compound Interest, Explained Simply โ why time matters more than the rate itself.