Free Interest Calculator - Simple & Compound Interest
Calculate both simple and compound interest instantly. Best free interest calculator 2025 for loans, savings, investments, and financial planning.
Quick Answer
An interest calculator computes how much interest you will earn (on savings) or pay (on loans) over time. Choose simple interest (I = PRT, on principal only) or compound interest (on principal plus accumulated interest). Our calculator at practicalwebtools.com shows both calculations for easy comparison.
Key Facts about Interest Calculator:
- Simple interest: I = P × R × T (principal only)
- Compound interest: A = P(1 + r/n)^(nt) (includes accumulated interest)
- Compound interest always yields more over time than simple interest
- Savings accounts typically use compound interest
- Some loans use simple interest; others use compound
- Higher compounding frequency = slightly more interest earned
- The difference between simple and compound grows over longer periods
Why Use Our Interest Calculator?
Comprehensive interest calculations:
Simple & Compound
Calculate both interest types in one place.
Side-by-Side Comparison
Compare simple vs compound interest results.
Flexible Periods
Calculate by days, months, or years.
Total Amount
See principal plus interest at any point.
Instant Results
Calculations happen immediately.
100% Private
Your data stays on your device.
How to Interest Calculator in 3 Easy Steps
Calculate any interest:
Enter Principal
Your starting amount.
Set Rate & Time
Interest rate and time period.
Choose Type
Simple or compound interest.
Understand Interest Completely
Compare simple vs compound interest
Calculate loan costs accurately
Plan savings growth over time
Make informed financial decisions
Common Use Cases for Interest Calculator
Essential for:
Frequently Asked Questions
Everything you need to know about our interest calculator
What is interest?
Cost of borrowing or reward for saving - calculated as % of principal.
Interest is the cost of borrowing money (paid on loans) or the reward for saving/investing money (earned on deposits). It is calculated as a percentage of the principal.
Should I use simple or compound interest?
Simple for short-term loans; compound for savings and long-term calculations.
Use simple interest for short-term, fixed-period loans. Use compound interest for savings accounts, investments, and most long-term calculations. Compound is more accurate for most real-world scenarios.
How often does interest compound?
Daily, monthly, quarterly, or annually - more frequent = slightly more interest.
Common compounding frequencies: annually (1x/year), quarterly (4x), monthly (12x), daily (365x). More frequent compounding = slightly more interest. Savings accounts often compound daily.
How do I calculate interest on a loan?
Simple: I = PRT. Compound: A = P(1+r/n)^(nt). Calculator does both.
For simple interest loans: I = Principal × Rate × Time. For compound interest: use A = P(1 + r/n)^(nt) then subtract principal. Our calculator handles both automatically.
Still have questions? Try the tool yourself!
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