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Finance Calculator FAQs
How is a monthly loan or mortgage payment calculated?
Monthly payment = P × [r(1+r)^n] / [(1+r)^n − 1], where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the number of months. Our calculators add property tax and insurance where relevant.
What is the difference between APR and interest rate?
The interest rate is the cost charged on the principal only. APR (Annual Percentage Rate) includes the interest rate plus fees such as origination, points and PMI, so it reflects the true yearly cost of borrowing and is better for comparing loans.
How much of my income should go toward debt?
A common guideline is the 28/36 rule: keep housing costs under 28% of gross monthly income and total debt under 36%. UK lenders typically cap mortgages at about 4–4.5× annual salary.
Do these calculators work for both the US and UK?
Yes. They accept any currency amount, interest rate and term, so they work for US and UK figures alike. Tax-specific tools (income tax, take-home pay) are labelled for the country they apply to.
Are these finance calculators free and private?
Yes — all are free, require no sign-up, and calculate entirely in your browser, so the numbers you enter are never sent to a server or saved.
Calculators localised for your country
Several of these tools have dedicated United States and United Kingdom versions, with the right currency, tax rules and terminology (USD, PMI, FHA & IRS for the US; GBP, deposit, LTV & HMRC for the UK).