Finance

Loans, savings and budgets all rest on a small set of ideas: interest accumulates on a balance, a fixed payment is split between interest and principal, and small differences in rate or term compound into large differences in total cost. The finance calculators here make those mechanics visible. The mortgage, auto-loan and loan-payment tools use the standard amortization formula; the savings and compound-interest tools show how regular contributions and compounding frequency change growth; the debt-to-income and home-affordability tools use the same ratios lenders use to size a loan.

Seeing the numbers side by side is often more useful than the single payment figure. A longer loan term lowers the monthly payment but raises the total interest paid. Paying a little extra each month shortens a credit card payoff far more than most people expect. A debt-to-income ratio that looks fine on paper may still leave a household with a tight monthly budget. We pair each calculator with a worked example and a plain-English explanation of the formula so you can check the logic rather than trusting a black box.

These tools are for education and planning. They use the inputs you enter, assume fixed rates and consistent payments, and do not include every fee, tax or insurance cost a real lender or tax authority would apply. For decisions with real money at stake, compare actual offers from lenders and consider speaking with a licensed financial professional or tax preparer.

Which calculator answers which money question

The sixteen tools in this category fall into a few natural groups, and choosing between them is easier once you know the question each one is built to answer. If you are borrowing, the Mortgage Calculator, Loan Payment Calculator and Auto Loan Calculator all return a monthly payment from an amount, a rate and a term, while the Amortization Calculator shows how every payment splits between interest and principal over the life of the loan. The Credit Card Payoff Calculator is a different animal: it simulates a revolving balance month by month, so use it when the question is how long a debt will last at a payment you choose.

If you are saving, the Savings Calculator projects a balance from a starting amount plus monthly contributions, and the Compound Interest Calculator tracks a single lump sum under different compounding frequencies. If you are testing whether a purchase is realistic, the Debt-to-Income Ratio Calculator and the Home Affordability Calculator turn your income and obligations into the ratios lenders review. For everyday arithmetic there are the Tip Calculator, Sales Tax Calculator and Discount Calculator. For income and spending, the Hourly to Salary Calculator, Paycheck Tax Calculator, Budget Calculator and the more detailed Budget Planner cover what comes in and where it goes.

A practical way to start is with the decision in front of you. Weighing two loan terms points to the payment and amortization tools, a job offer points to hourly-to-salary and paycheck tax, and a big purchase usually needs affordability, debt-to-income and a payment calculator together. The matching guides on this site, covering mortgage payments, amortization, compound interest, paychecks and the 50/30/20 rule, walk through the same formulas in prose.

Amortization: why early payments are mostly interest

A fixed-rate loan has a constant payment, but the split inside it changes every month. Interest each month is the remaining balance times the monthly rate, and whatever is left of the payment reduces principal. Take a 320,000 dollar mortgage at 6.5 percent over 30 years, a purely illustrative rate. The monthly principal and interest comes to about 2,022.62 dollars. In the first month, interest is 320,000 times 0.065 divided by 12, or 1,733.33 dollars, so only about 289 dollars of that first payment reduces the balance. The proportion shifts slowly at first and faster later, because each small principal reduction lowers the next month's interest.

The cost of the long term is easy to see side by side. On the same loan, a 15-year term raises the payment to about 2,787.54 dollars but cuts total interest from roughly 408,000 dollars to roughly 182,000. A 20-year term sits between them, near 2,385.83 dollars a month. None of these numbers include property tax, insurance or HOA dues, which the Mortgage Calculator lets you add as flat monthly amounts, and none include closing costs or any mortgage insurance a lender may require.

The same logic applies to every installment loan, which is why the Loan Payment, Auto Loan and Amortization calculators share a formula. Two loans with the same rate and term have the same percentage shape and differ only in dollar scale, so the pattern you see on a small loan is the pattern on a large one.

Paying down debt: cards, cars and the cost of time

A credit card behaves differently from an installment loan because the balance and the payment are both under your control. The Credit Card Payoff Calculator charges interest each month at the APR divided by 12, subtracts your payment, and repeats until the balance reaches zero. On a 5,000 dollar balance at 22 percent APR, a fixed 200 dollar payment clears the debt in about 34 months with roughly 1,750 dollars of interest. Raise the payment to 250 dollars and the payoff drops to about 26 months and roughly 1,290 dollars of interest; cut it to 150 dollars and it stretches to about 52 months and nearly 2,800 dollars. If your payment is no larger than the first month's interest, the balance never falls, and the tool says so.

Auto loans show the term trade-off in a smaller package. Financing 28,000 dollars at 7 percent costs about 554 dollars a month over 60 months and about 477 over 72. The longer term feels cheaper monthly but adds roughly 1,100 dollars of total interest, from about 5,266 to about 6,371 dollars. The Auto Loan Calculator also folds in sales tax, trade-in value and down payment before it amortizes the amount financed, and it assumes tax on the full vehicle price, which is how most states compute it but not all.

Growing money: contributions, time and compounding

Saving is the mirror image of borrowing. The Savings Calculator assumes interest compounds monthly and contributions arrive at the end of each month. Setting aside 300 dollars a month at 4 percent for 10 years puts in 36,000 dollars and ends near 44,175, so about 8,175 dollars is interest. Starting with 2,000 dollars already saved lifts the end balance to roughly 47,157, and raising the monthly amount to 400 dollars gives about 58,900. Because both rate and time work on the balance, the earliest contributions do the most work, which is why starting sooner often matters more than finding a slightly higher rate.

Compounding frequency is the smaller lever, and the Compound Interest Calculator makes that visible. A 10,000 dollar lump sum at 5 percent for 20 years grows to about 26,533 dollars with annual compounding, about 27,126 with monthly, and about 27,181 with daily. More frequent compounding helps, but the gap between monthly and daily is small compared with the gap between 20 years and 10. The tool applies one constant rate, so it cannot model a promotional rate that steps down or a market-linked return that varies year to year.

Affordability, paychecks and everyday price math

Lenders look at income before they look at a house. The Debt-to-Income Ratio Calculator divides monthly debt payments by gross monthly income and sorts the result into bands: 20 percent or below is labeled excellent, 20 to 36 good, 36 to 43 moderate, and above 43 high. The Home Affordability Calculator applies the common 28 and 36 guideline, meaning housing costs near 28 percent of gross income and total debts near a back-end limit you choose, 36 percent in its conservative setting. With 6,000 dollars of gross monthly income, 28 percent is 1,680 dollars, while 36 percent minus 500 dollars of other debts leaves 1,660, so the tighter limit governs. Individual lenders and loan programs set their own cutoffs.

For income, the Hourly to Salary Calculator multiplies rate by weekly hours and weeks worked: 25 dollars an hour at 40 hours for 52 weeks is 52,000 dollars, and 50 weeks drops it to 50,000. The Paycheck Tax Calculator annualizes one paycheck, subtracts pre-tax deductions and the standard deduction, and applies marginal brackets, which means each additional dollar is taxed only at the rate of the bracket it falls in. It subtracts no tax credits. For prices, a 20 percent discount followed by 10 percent off is 28 percent off, not 30, and sales tax can be backed out of a receipt by dividing the total by one plus the rate.