Free Online Calculator Tools

About Calculator tools

Each calculator here does one job: percentage, date difference, loan, compound interest. Enter the numbers you know and get the answer together with the working, so you can check it.

Everything runs in your browser. Numbers you type, including salary, mortgage and investment figures, never leave your device. Results copy with one click, and some tools let you export the full working.

How to choose the right Calculator

1. Start from the question

   Share, growth rate and amortisation are different problems with different inputs. Name the problem first, then pick the tool.

2. Prefer tools that show the working

   A bare answer is hard to check. Most calculators here display intermediate values, like the principal and interest split inside a monthly payment.

3. Check the convention

   Annual or monthly rate, calendar or working days: the result changes a lot. Read the note on the tool before you trust the output.

4. Keep sensitive figures local

   For anything involving income or debt, use tools that run locally. Every calculator in this category computes in your browser.

Common calculator mistakes

1. Precise is not correct

   A calculator computes exactly what you feed it. Pick the wrong convention, like reading a monthly rate as annual, and the answer is precisely wrong. Confirm units first.

2. More decimals, more truth

   Eight decimal places do not fix fuzzy inputs. Output cannot carry more real precision than the input has. Round for the decision you are making.

3. One formula fits all

   Loans, compound interest and taxes each carry assumptions. Prepayments and bracket changes need matching modes; forcing the basic formula misleads.