Smart money calculators for life’s biggest decisions
Free mortgage, loan, salary and investment calculators built for the USA and UK. No sign-up, no tracking — your numbers never leave your browser.
- Twelve specialised tools
- Built for the USA & UK
- Runs 100% in your browser
Calculators
Start with the decision, not a spreadsheet.
Pick the question you are trying to answer. Every tool shows the headline number first, then gives you the breakdown behind it.
Mortgage Calculator
Estimate monthly payments, total interest and see a full amortisation schedule — at today’s rates.
Calculate →Home Affordability Calculator
Work out how much house you can afford using the 28/36 rule.
Calculate →Rent vs Buy Calculator
Compare the true 5-year cost of renting against buying a home.
Calculate →Refinance Calculator
Compare your current loan with a new one and find your break-even point.
Calculate →Closing Costs Calculator
Estimate the 2–5% in fees due on closing day, itemised line by line.
Calculate →Salary Calculator
Turn a US gross salary into take-home pay after federal, state and FICA taxes.
Calculate →Loan Calculator
Monthly payments and total interest for personal and auto loans.
Calculate →Compound Interest Calculator
Watch your savings grow with contributions, plotted on a chart.
Calculate →Retirement Calculator
Project your nest egg from your age, savings and monthly contributions.
Calculate →Rental Yield Calculator
Cap rate, cash-on-cash return and monthly cash flow for investors.
Calculate →Credit Card Payoff Calculator
Enter up to 3 cards and a monthly budget — see your debt-free date, total interest and snowball vs avalanche.
Calculate →Mortgage Recast Calculator
Put a lump sum toward your mortgage — see your new lower payment, monthly savings and interest saved.
Calculate →Latest guides
Fresh money maths, in plain English.
From the blog — worked examples with real numbers.
Estate Planning
How to Contest a Will: Grounds, Standing & Process
Who can challenge a will, on what grounds, and by when — standing, state deadlines, the process, and the costs.
Read guide →
Retirement
Average Retirement Savings for Married Couples by Age
Combined household savings by age band: Fidelity targets versus what married couples actually hold, and how to catch up.
Read guide →
Retirement
What Is a Backdoor Roth IRA? A 2026 Step-by-Step Guide
The legal two-step that gets high earners into a Roth IRA — the process, the pro-rata trap, and the 2026 limits.
Read guide →Why My Knowledge Dock
Serious decisions deserve better than guesswork.
Three promises behind every page on this site.
Built for accuracy
Every calculator uses the standard financial formulas lenders and planners rely on — amortisation, marginal tax brackets and time value of money.
Private by design
All maths runs locally in your browser with plain JavaScript. Your income, debts and home prices are never sent to our servers.
Free, no sign-up
Every tool is free to use as often as you like. No accounts, no paywalls, no limits.
Make confident money decisions
Buying a home, taking out a loan or negotiating a salary are among the largest financial decisions most people ever make — yet they usually hinge on a single number: the monthly payment. My Knowledge Dock exists to make that number transparent. Instead of relying on a lender’s headline figure, you can test scenarios yourself: what happens if rates rise by half a point, if you put 10% down instead of 20%, or if you refinance two years from now?
Our tools are designed for readers in the United States and the United Kingdom. Use the currency switcher on any calculator to view results in dollars or pounds. A few tools are country-specific — the salary calculator models US federal and state taxes, for example — and those pages say so clearly. Wherever figures are simplified or estimated, we label them as estimates.
How the calculators work
Each calculator is a small, self-contained program that runs entirely in your web browser. There is nothing to install and no account to create. Type in your numbers and the results update instantly, including detailed breakdowns such as year-by-year amortisation schedules and growth charts. Because nothing is sent over the internet, you can use the tools offline once the page has loaded — and your financial details stay on your device.
Frequently asked questions
Are these calculators really free?
Yes. Every calculator on My Knowledge Dock is free to use with no account or sign-up, and there are no usage limits.
How accurate are the results?
The calculators use standard financial formulas — for example, the same amortisation formula lenders use for mortgages. Results are estimates for planning purposes and are not financial advice. Taxes, insurance and fees vary by location and lender, so treat outputs as a starting point for conversations with a professional.
Is my financial data private?
Yes. All calculations happen locally in your browser using JavaScript. We never see, store or transmit the numbers you enter.
Do the calculators work for the UK as well as the US?
Mostly, yes. Every calculator has a USD/GBP currency switcher. The salary calculator is US-specific because it models US federal tax brackets, and a few pages note US/UK differences in the guidance text.