Free finance calculators

How in-browser finance calculators work

The math behind a mortgage payment, a loan schedule, or a compound-interest projection is simple enough to run directly in JavaScript on your machine. None of these tools need a server. The numbers you type are read by the page's script, the calculation runs, and the result is displayed. Our servers are not involved at any point.

Calculations are estimates for informational purposes. They follow the standard formulas documented on each tool page (amortisation schedules, future-value formulas, a single user-set effective tax rate). For decisions with real money on the line, talk to a qualified professional.

The formulas behind each calculator

The mortgage and loan calculators both implement the standard amortization formula M = P[r(1+r)^n] / [(1+r)^n - 1], where P is the loan amount, r is the monthly interest rate (annual rate divided by twelve), and n is the total number of monthly payments. For mortgages, optional property tax and home insurance are added on top to produce a full PITI figure. The loan tool also shows a visual split of principal versus interest across the life of the loan.

The salary calculator converts between hourly, weekly, bi-weekly, monthly, and annual pay using the 40 x 52 default schedule (2,080 working hours per year), with sliders to adjust hours per week and weeks per year for non-standard arrangements. The take-home slider applies a single user-chosen effective tax rate as a planning estimate.

The ROI calculator implements three modes: simple ROI as ((gain - cost) / cost) x 100, annualized ROI as ((gain / cost)^(1 / years) - 1) x 100, and marketing ROI applied to ad spend and attributed revenue. The compound interest calculator uses A = P(1 + r/n)^(nt) and includes a year-by-year breakdown table.

All math is plain JavaScript with no external library, and each formula is short enough to update the result as you type.

In-browser finance calculators vs the alternatives

Each option answers a different question. The in-browser calculators give a standard-formula estimate the moment you type, and a spreadsheet suits a model you want to keep and extend. For advice on a real decision, speak to a qualified financial professional.

When to use these tools

• House hunting? Estimate your monthly payment with the mortgage calculator, including an amortization schedule, then compare any auto or personal loan using the loan calculator.
• Comparing a job offer? Convert between hourly, weekly, monthly, and annual figures with the salary calculator and estimate the take-home pay.
• Planning long-term savings? Project growth using the compound interest calculator, which includes a year-by-year breakdown.
• Measuring a marketing campaign or investment? Work out the return with the ROI calculator, which supports simple and annualized modes.
• Shopping a sale? See exactly how much you save and what you pay with the discount calculator, including stacked percent-off offers.

Frequently asked questions

Are these finance tools free?

Yes. Every calculator on this page is free to use. There is no account, no email signup, and no premium tier. Enter your numbers and the result appears immediately.

How accurate are the calculations?

Each calculator implements a standard, widely used finance formula directly in JavaScript. Mortgage and loan tools use the standard amortization formula M = P[r(1+r)^n] / [(1+r)^n - 1]. Compound interest uses A = P(1 + r/n)^(nt). ROI uses ((gain - cost) / cost) x 100. The calculators use standard JavaScript numbers and show results rounded to two decimal places. Results are estimates for planning purposes only.

Do you store any financial data I enter?

All calculations run as JavaScript inside your browser. The loan amounts, interest rates, salaries, and other figures you enter are used only for the calculation in that browser tab. They are not saved or logged, and they are not sent to our servers.

What disclaimer applies to these calculators?

All finance tools on this site provide estimates for informational purposes only. They are not financial advice and do not account for every factor that affects a real-world loan, investment, or paycheck. Consult a qualified financial professional before making financial decisions.

Why do salary tools not include exact tax tables?

Tax rates vary by country, region, employment status, deductions, and benefits. Rather than ship out-of-date local tax tables, the salary calculator lets you enter your own effective tax rate to produce a rough take-home estimate. Use a dedicated payroll calculator for precise figures in your jurisdiction.

Can I use these tools offline?

Once a calculator's page has loaded, yes, in that tab. Every calculation runs in the page, so you can disconnect and keep using the calculator until you close or reload the tab or open another page. Opening or reloading a page needs a connection, because the site installs no service worker and the browser checks each page with the server as it opens.