Finance & Business Calculators
Loans, mortgage, ROI, retirement, taxes and savings.
Twenty calculators for borrowing, saving, retirement, tax and return, and every one of them shows the total as well as the payment. On a long loan those two numbers tell opposite stories, which is the single most useful thing this category has to say.
All 20 finance & business calculators
One idea runs through all of them
Almost every tool on this page is the same principle in a different costume: money has a time value. A dollar now is worth more than a dollar later, and compounding is what turns that difference into the numbers that actually decide things. Borrowing is compounding working against you; saving and investing is the same maths on your side.
This is why the monthly payment is the least interesting output on a loan. A longer term always lowers the payment and always raises the total, and the gap is not small. Judging two loans by their payments systematically picks the more expensive one.
Which calculator answers which question
| Your question | Start with |
|---|---|
| What will the payment be? | Loan or mortgage calculator |
| What can I afford to borrow? | Home affordability |
| How fast can I clear this debt? | Debt payoff or credit card payoff |
| Is refinancing worth it? | Refinance |
| What will I actually take home? | Take-home pay |
| Will I have enough to retire? | Retirement and 401(k) |
| What is this investment returning? | ROI and compound interest |
Three places these numbers mislead people
The payment is not the cost. Comparing two loans on their monthly payment alone rewards whichever has the longer term. Compare total interest paid, and treat the payment as a constraint on your monthly budget rather than a measure of value.
Reversing a percentage is a division, not a subtraction. Backing tax out of a tax-inclusive total is total ÷ (1 + rate), and pricing to a target margin is cost ÷ (1 − margin). Subtracting the percentage instead is always wrong in the same direction, and it always understates. The same mistake appears in three unrelated places, so it is worth learning to recognise.
Small rate differences compound into large ones. Over a thirty-year horizon, one percentage point of annual return is not one percent more money; it is often a third more. The retirement and compound interest calculators show that gap directly, and starting age moves it further than contribution rate does.
Estimates, not advice
Every figure here is a planning estimate. The tax tools use current federal figures and a flat state rate, and they ignore credits, local taxes and filing statuses beyond single and married filing jointly. Nothing on this site is financial or tax advice, and no qualifications are claimed for it. What each page does give you is the full method it used, with its sources linked, so you can check the number rather than trust it.
Finance & Business Calculators: common questions
Which calculator should I use to compare two loans?
The loan calculator, and compare total interest rather than the monthly payment. A longer term always produces a lower payment and a higher total cost, so payment-only comparisons systematically favour the more expensive loan.
Are these finance calculators accurate?
They use standard formulas, and each page states its assumptions and constants with sources. They are planning estimates rather than quotes. Real offers include fees, insurance, local taxes and lender-specific terms no general calculator can know.
Do the tax calculators use current figures?
Yes. The federal brackets, standard deduction and Social Security wage base are held on the current tax year and re-checked each October when the IRS and SSA publish, with both sources linked on the page.
What matters most for retirement, the amount or the start date?
The start date, by a wide margin. Contributions made early compound for decades, so beginning ten years sooner typically beats contributing considerably more later. The retirement calculator shows the difference by starting age.