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Math of Money

Savings & Investing Calculators

See how compounding turns regular contributions into long-term growth, project a lump-sum or recurring investment, or work backward from a savings goal to the monthly amount you need to set aside.

Compound Interest CalculatorHow savings grow with regular contributions.Investment CalculatorProjected growth of a lump sum or recurring investment.Savings Goal CalculatorWhat to save monthly to hit a target by a target date.CD CalculatorCertificate of deposit earnings, APY, taxes, and early-withdrawal penalties.Inflation CalculatorWhat a dollar from any year since 1913 is worth today, and future costs.Net Worth CalculatorAdd up your assets and liabilities to see your net worth and debt-to-asset ratio.Currency ConverterConvert between 40+ currencies with live exchange rates.

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Frequently asked questions

What's the difference between simple and compound interest?

Simple interest is earned only on the original principal; compound interest is earned on the principal plus previously earned interest, which is why time matters so much.

How much difference does contribution frequency make?

Contributing monthly instead of annually slightly increases growth because money is invested sooner, though the effect is smaller than the impact of the contribution amount or time horizon.

What rate of return should I use for stocks?

Many planners use 6–7% annually after inflation for a diversified stock portfolio as a conservative long-run estimate, but you can adjust it to test other scenarios.

How much do I need to save monthly to reach my goal?

The Savings Goal calculator works backward from your target amount, timeline, and expected return to show the required monthly contribution.

Does the investment calculator account for taxes or fees?

You can enter an expected fee or expense ratio; taxes on gains depend on the account type, so results are shown pre-tax — treat them as an upper bound for taxable accounts.

Is it better to invest a lump sum or contribute regularly?

Historically, investing a lump sum immediately tends to outperform spreading it out, since markets rise more often than they fall — but regular contributions reduce the risk of bad timing.