Finance calculator
Interest Calculator
Calculate simple or compound interest and estimate final account value.
Quick answer
How do you calculate compound interest?
Use A = P(1 + r/n)^(nt), where P is the starting amount, r is the annual rate as a decimal, n is compounding periods per year, and t is years. $1,000 at 5% compounded monthly for 10 years grows to about $1,647.
Simple: A = P(1 + rt) • Compound: A = P(1 + r/n)^(nt)
⚡ Answer updates as you type · Enter = calculate · Esc = reset
The Interest Calculator estimates simple or compound interest earned over time and the final account balance.
Disclaimer: This tool provides estimates for informational purposes only and is not financial advice. Please do your own due diligence and consult a qualified professional before making real-world financial decisions.
About this Interest Calculator
Calculate simple interest or compound interest on savings, investments, or loans. See how compounding frequency dramatically changes long-term growth.
What you'll need
- • Principal
- • Annual interest rate
- • Time in years
- • Compounding frequency
How it works
- 1. Choose simple or compound interest.
- 2. Enter principal, rate, and time.
- 3. Pick compounding frequency for compound interest.
- 4. View final value and total interest earned.
Worked example
$10,000 at 5% compounded monthly for 10 years grows to $16,470, vs. $15,000 with simple interest.
Related searches
Interest Calculator FAQ
What is the Interest Calculator?
The Interest Calculator is a free online tool that helps you calculate simple or compound interest and estimate final account value.
How do I use the Interest Calculator?
Open the Interest Calculator, enter the requested values, and review the instant estimate on the page.
Is the Interest Calculator free?
Yes. The Interest Calculator is free to use on Fast Online Calculator and does not require an account.
What is the difference between simple and compound interest?
Simple interest is calculated only on the original principal. Compound interest is calculated on principal plus previously earned interest, which accelerates growth.
Which compounding frequency is best?
More frequent compounding (daily > monthly > yearly) produces slightly higher returns on savings and slightly higher cost on debt.
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