Interest Calculator

The Interest Calculator supports two modes. Fixed investment grows a single lump sum at a stated rate. Periodic contributions add deposits each...

Modify the values and click the Calculate button to use.
Results

Enter values and click Calculate.

Schedule

Related: Compound Interest CalculatorInterest Rate CalculatorInvestment CalculatorFinance Calculator

Introduction

The Interest Calculator supports two modes. Fixed investment grows a single lump sum at a stated rate. Periodic contributions add deposits each period—ideal for payroll savings or monthly investing.

Fixed vs Periodic Contributions

The Interest Calculator supports two modes. Fixed investment grows a single lump sum at a stated rate. Periodic contributions add deposits each period—ideal for payroll savings or monthly investing.

Compounding Frequency

Select annual, semi-annual, quarterly, monthly, weekly, or daily compounding. More frequent compounding slightly increases ending balance at the same nominal rate. APY already embeds compounding; use APR when the tool asks for a nominal annual rate.

Beginning vs End of Period

Deposits at the beginning of each period earn a full period of growth. End-of-period deposits are the standard assumption for many savings accounts. The difference grows with rate and horizon.

Reading the Schedule

The period-by-period table shows starting balance, interest earned, deposits, and ending balance. Use it to verify when your interest income exceeds contributions—a milestone for long-term investors.

Tax and Inflation Context

Quoted rates are usually pre-tax. Taxable accounts reduce net returns; tax-advantaged accounts may defer or eliminate some drag. Adjust expectations with our Inflation Calculator for real purchasing power.

Related Calculators

See also the Savings Calculator (goal-based deposits), Investment Calculator (return and inflation), and CD Calculator for fixed-term deposits.

How It Works

  1. Enter your amounts, rates, and term in the form. Use the same units shown in the labels (dollars, years, percent).
  2. Click Calculate to run the Interest Calculator engine. Invalid or empty required fields show a clear error message.
  3. Review the summary cards for the key outputs. Expand schedules or tables when available for period-by-period detail.
  4. Copy, print, or share your scenario link. Reset the form anytime to start a fresh comparison.

Formula

Future Value with compounding: FV = P(1 + r/n)^(nt). For periodic deposits, each contribution grows from its deposit date at the same periodic rate.

FAQ

Yes. CDCalculator.io provides the Interest Calculator at no charge for personal and educational use. Results are estimates and not financial advice.

The tool uses standard formulas lenders and planners use in spreadsheets. Your bank may round differently or include fees not modeled here.

Use the Copy Results and Print buttons on the calculator panel after you run a scenario. You can also share the page link with colleagues.

Focus on realistic rates, terms, and any extra payments or contributions. Small changes in APR or time horizon often move outcomes more than rounding.

No. Use this calculator to explore scenarios, then consult a qualified advisor or lender for decisions about investment products.