Free Finance Calculators

How to get accurate results

A finance calculator is only as good as the assumptions behind it. A few details make the difference between a number you can plan around and one that misleads you:

Match the compounding frequency to your account

Interest that compounds monthly grows faster than the same rate compounding annually. Savings accounts and most loans compound monthly; some bonds and CDs compound semi-annually. Our compound interest calculator lets you set the frequency, and the gap over 20–30 years is larger than most people expect.

Use APR to compare, the interest rate to budget

When you are shopping for a loan, compare offers by APR, because it includes fees and reflects the true yearly cost. When you are estimating a monthly payment, the nominal interest rate is what drives the amortization schedule. Confusing the two is the most common mistake we see — a low rate with high fees can cost more than a higher rate with none.

Separate nominal returns from real returns

An investment that returns 7% a year while inflation runs at 3% is really growing your purchasing power by about 4%. If a long-term plan ignores inflation, it overstates what your money will buy. Pair the retirement calculator with the inflation calculator to see both the headline balance and what it is actually worth.

Total interest matters more than the monthly payment

Stretching a loan over more years lowers the monthly payment but usually raises the total interest paid — sometimes dramatically. Before choosing a longer term, check the lifetime cost in the loan comparison tool, and see how extra payments shorten the timeline in the debt payoff calculator.

Which calculator should you use?

Most money questions map to one of a few calculations. Here is how to pick:

• "What will my monthly payment be?" — a loan or mortgage calculator. You need the amount, rate, and term; it returns the payment and the amortization split.
• "Which of these two offers is cheaper?" — the APR calculator (to normalize for fees) and loan comparison (to see lifetime cost).
• "How much will my savings grow?" — the compound interest calculator for a lump sum or regular contributions, and the retirement calculator for a long-horizon goal.
• "How long until this debt is gone?" — the debt payoff calculator, which also shows the interest saved by paying extra.
• "Does this product or price actually make money?" — the break-even and profit margin calculators.

Worked examples

These illustrate the math the calculators run. Numbers are rounded; your inputs and current rates will differ.

A 30-year mortgage

Borrow $300,000 at a 6% annual rate over 30 years. The monthly payment works out to about $1,799. Over the full term you repay roughly $647,600 — meaning about $347,600 is interest, more than the original loan was for. This is why shaving years off the term, or paying a little extra each month, changes the lifetime cost so dramatically.

Compounding over 30 years

Leave $10,000 untouched at a 7% annual return for 30 years and it grows to about $76,100 — more than seven times the original, with none of it from new contributions. Start ten years later and the same $10,000 reaches only about $38,700. The decade, not the deposit, is doing the work.

Why APR and APY differ

A 12% nominal rate compounded monthly is not really 12% a year. Because each month's interest earns interest of its own, the effective annual rate (APY) is about 12.68%. Lenders quote the lower nominal figure; savers should look at the higher effective one. The APR calculator handles this conversion.

Key terms, briefly

• Principal — the amount borrowed or invested, before any interest.
• Amortization — how each loan payment splits between interest and principal. Early payments are mostly interest; later ones mostly principal.
• APR vs APY — APR is the yearly cost of a loan including fees; APY is the effective yearly return on savings including compounding.
• Nominal vs real return — nominal is the headline rate; real subtracts inflation to show change in purchasing power.
• Compounding frequency — how often interest is added to the balance (monthly, quarterly, annually). More frequent compounding means faster growth at the same rate.

Finance guides

Short, plain-English explainers that go deeper than the calculators:

Frequently asked questions

Are these finance calculators accurate?

Yes. Each uses the standard financial formula — amortization for loans, the compound interest formula for investments, effective-rate math for APR. Because results depend on your inputs and on rates that change in the real world, treat them as planning estimates rather than a quote from a lender.

Is my financial data private?

Every calculation runs entirely in your browser. Nothing you type — salary, loan balance, savings — is sent to a server or stored anywhere. Once the page has loaded you can even use the tools offline.

What is the difference between APR and the interest rate?

The interest rate is the cost of borrowing the principal. APR folds in fees and certain closing costs, so it reflects the true yearly cost of the loan. Two loans with the same interest rate can have very different APRs.

Why does compounding frequency change the result?

The more often interest is added to the balance, the sooner it starts earning interest of its own. Monthly compounding therefore beats annual compounding at the same nominal rate, and the difference grows over long periods.

Do I need to sign up or pay?

No. All 15 finance calculators are free, with no account, email, or payment required.