A set of finance calculators that run entirely in your browser. Calculate mortgage payments, loan amortization for cars, personal loans, and student debt, convert between hourly and annual salary, work out the return on an investment or marketing spend, and project compound interest growth over any timeframe.
All Finance tools provide estimates for informational purposes only. Consult a financial professional for advice. The calculations use standard, widely published formulas implemented in plain JavaScript that runs locally on your device. No loan amounts, salaries, or other figures you enter are sent to any server.
Read the complete finance tools guide
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. Closing the tab clears the inputs from memory, and nothing was transmitted in the first place.
Calculations are estimates for informational purposes. They follow the standard formulas documented on each tool page (amortisation schedules, future-value formulas, marginal rate brackets). For decisions with real money on the line, talk to a qualified professional.
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 additionally 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 done in standard JavaScript with no external library. The formulas are simple enough that there is nothing to outsource to a server, and the privacy benefit of keeping the numbers local is real.
| Approach | Privacy | Saves history | Best for |
|---|---|---|---|
| In-browser (this site) | All local | No | Quick estimates, sanity checks, scenario comparisons |
| Online finance sites | Server-side, often with tracking | Sometimes | When you do not mind sharing the numbers |
| Spreadsheets | Local file, cloud sync optional | Yes | Custom scenarios and long-term tracking |
| Financial professional | Client confidentiality | Yes (in your file) | Actual financial advice and tax planning |
These options answer different questions. Use the in-browser calculators when you want a fast number without sharing financial details. Build a spreadsheet for ongoing planning. Speak to a qualified professional for advice on real decisions.
Calculations are estimates for informational purposes only. Consult a financial professional for advice.