What is the difference between simple and compound interest?

Simple interest is calculated only on the principal amount, while compound interest is calculated on the principal plus any accumulated interest. Compound interest grows faster because you earn interest on your interest.

How often should interest be compounded for best results?

For savings and investments, more frequent compounding (daily or continuous) yields higher returns. The difference between monthly and daily compounding is usually small, but over long periods it adds up. Our free calculator lets you compare all compounding frequencies.

What is the Rule of 72?

The Rule of 72 is a quick way to estimate how long it takes to double your money. Simply divide 72 by your annual interest rate. For example, at 6% interest, your money doubles in approximately 12 years (72÷6=12).

What is the difference between APR and APY?

APR (Annual Percentage Rate) is the simple interest rate without compounding. APY (Annual Percentage Yield) includes the effect of compounding and shows the actual yearly return. APY is always equal to or higher than APR when interest compounds.

Is this interest calculator really free?

Yes! This interest calculator is 100% free with no signup, no subscription, and no hidden fees. FreeWWW.com provides free tools and utilities to help everyone with their financial planning needs.

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Interest Calculator

Calculate simple and compound interest, plan your savings, analyze loans, and reach your financial goals — all 100% free!

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Savings & Investment Calculator

Interest Type

Initial Deposit (Principal)

Compound Frequency

Time Period

Time Unit

💵 Regular Contributions (Optional) ▼

Contribution Amount

Frequency

Contribute at beginning of period

📉 Inflation Adjustment (Optional) ▼

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Results

Final Balance

$0.00

Total Principal

$0.00

Total Interest Earned

$0.00

APY (Effective Rate)

0.00%

Interest/Principal Ratio

0.00%

📋 Year-by-Year Breakdown ▼

Year	Starting Balance	Contributions	Interest	Ending Balance

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Loan Calculator

Loan Amount

Loan Term

Term Unit

Payment Frequency

💰 Extra Payments (Optional) ▼

Extra Payment Amount

Extra Payment Frequency

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Loan Summary

Monthly Payment

$0.00

Total Principal

$0.00

Total Interest

$0.00

Total Cost of Loan

$0.00

Payoff Date

📋 Amortization Schedule ▼

Payment #	Payment	Principal	Interest	Balance

Scenario A

First Scenario

Principal

Annual Rate

Compounding

Time (Years)

Monthly Contribution

Scenario B

Second Scenario

Principal

Annual Rate

Compounding

Time (Years)

Monthly Contribution

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Comparison Results

Scenario A Final Balance

$0.00

Scenario B Final Balance

$0.00

Difference

$0.00

Final Balance Comparison

A: 50%

B: 50%

Enter values to compare

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Savings Goal Planner

Target Amount (Goal)

Current Savings

Expected Annual Return

Time to Goal (Years)

Contribution Frequency

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Goal Analysis

Required Contribution

$0.00

per month

Total Contributions

$0.00

Interest Earned

$0.00

Starting Balance Grows To

$0.00

Contribution Growth To

$0.00

📋 Year-by-Year Progress ▼

Year	Contributions	Interest	Balance	Progress

⏱️ Rule of 72 Calculator

Estimate how long it takes to double your money at a given interest rate.

Annual Interest Rate

years to double

Rule of 72: 72 ÷ rate = years to double
Rule of 69.3: More accurate for continuous compounding

🔄 APR to APY Converter

Convert between Annual Percentage Rate and Annual Percentage Yield.

Enter Rate

Compounding Frequency

Conversion Direction

APY

📅 Present Value Calculator

Calculate the present value of a future sum of money.

Future Value

Discount Rate

Years

present value today

📈 Future Value Calculator

Calculate what today's money will be worth in the future.

Present Value

Interest Rate

Years

future value

💵 Simple Interest Calculator

Quick calculation for simple (non-compounding) interest.

Principal

Annual Rate

Time (Years)

total interest

Final Amount: -

🎯 Rate Finder

Find the interest rate needed to reach a goal.

Starting Amount

Target Amount

Time Period (Years)

annual rate needed

How to Use This Tool

Choose a calculator tab — Select from Savings Calculator, Loan Calculator, Comparison Tool, Goal Planner, or Quick Tools.
Enter your values — Fill in principal, interest rate, time period, and compounding frequency.
Calculate — Click the Calculate button to see detailed results with year-by-year breakdowns.
Compare scenarios — Use the Comparison tab to evaluate different rates, terms, or compounding frequencies side by side.
Plan your goals — Use the Goal Planner to figure out how much to save monthly to reach a target amount.
Quick conversions — Use the Quick Tools tab for APR-to-APY conversion, rule of 72, and other fast calculations.

Common Use Cases

How much will my savings grow with compound interest? Enter your deposit amount, interest rate, and time period to see projected growth with a detailed breakdown.
What will my loan payments be? Use the Loan Calculator to find monthly payments, total interest paid, and a full amortization schedule.
What is the difference between APR and APY? Use the Quick Tools tab to convert between APR and APY and understand how compounding frequency affects your effective rate.
How long will it take to double my money? Enter your interest rate in the Quick Tools rule-of-72 calculator for an instant estimate.
How much do I need to save each month to reach my goal? Use the Goal Planner with your target amount and timeline to calculate the required monthly contribution.

📊 How to Use This Calculator

How to Use This Tool

Common Use Cases