Compound Interest Calculator

Calculate how your money grows with interest! Enter your principal, rate, compounding, and contributions—get full results & visualizations instantly.
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Initial investment

Annual contribution

Contribution frequency

Contribution timing

End of period Beginning of period

Interest rate

Compound

Investment length

years

Tax rate (optional)

Inflation rate (optional)

Results

Ending balance: $0.00
Total principal: $0.00
Total contributions: $0.00
Total interest: $0.00
Interest of initial investment: $0.00
Interest of contributions: $0.00
Buying power after inflation: $0.00

Accumulation Schedule

Year	Deposit	Interest	Ending balance

Learn About Interest

Interest Explained

Interest is what you earn from savings or what you pay for borrowing. There are two main types of interest: simple interest and compound interest.

Simple Interest

Simple interest is calculated only on the original amount (the principal). For example, borrowing $1000 at 10% annual simple interest for 2 years:

Year 1: $1000 × 10% = $100
Year 2: $1000 × 10% = $100
Total interest after 2 years: $200
Total owed: $1200

The formula: Simple Interest = Principal × Rate × Term

Compound Interest

Compound interest means you earn interest on both your principal and previous interest. Using the same $1000 at 10% for 2 years, compounded annually:

Year 1: $1000 × 10% = $100 → New balance: $1100
Year 2: $1100 × 10% = $110
Total interest after 2 years: $210
Total owed: $1210

The main compound formula: A = P(1 + r/n)^nt
Where P = principal, r = annual rate, n = compounding per year, t = years.

Contribution, Taxes, & Inflation

Contribution Timing: Contribute at the beginning or end of each period (end is most common for savings).
Tax on Interest: Some earnings are taxable. Our calculator can estimate after-tax results.
Inflation: Rising prices may erode real returns. The calculator compares your end balance with its “buying power” after inflation.

Compounding Frequency and the Rule of 72

The more often interest is compounded (monthly, daily, etc.), the faster your balance grows.
Rule of 72: Years to double = 72 ÷ Interest Rate (%) (Approximate!)
Example: At 6% interest, money doubles in about 12 years (72/6 = 12).