What this site is
Capital Calculators is a free collection of 33 calculators and a set of plain-English guides covering loans, saving, investing and business finance. It exists to make one thing easy: turning a money question into a clear number you can act on.
How the calculators are built
- Standard formulas. Each tool uses the textbook formula for its job, such as the fixed-payment amortization formula for loans or discounted cash flow for NPV. The formula is shown on the page.
- A worked example on every page. The example is produced by the calculator itself, so the numbers in the text always match what the tool returns.
- Tested against known results. Calculations are checked against hand-worked cases and edge cases, such as a zero interest rate or a payment too small to cover interest.
- Private by design. The maths runs in your browser. The values you enter are not sent to us.
What the results are, and are not
Results are estimates for education and planning. They leave out things the calculator cannot know, such as your tax position, lender fees not entered, or how markets will behave. Nothing here is financial, tax or legal advice.
Corrections
If you find an error or have an idea for a calculator, write to hello@capitalcalculators.com. Corrections are reviewed and fixed quickly.