About
Craig's Tool Box is a free collection of online calculators, converters, generators and everyday utilities. Every tool does one job, opens instantly and works right in your browser, with no account, no download and no fee.
Why this site exists
Most people need a quick answer several times a week: what a mortgage will really cost, how many inches are in 170 centimeters, whether a password is strong enough, how long a speech will take to read. Too often those answers are buried in cluttered pages full of pop-ups. We build each tool to be fast, readable and easy to use on a phone, and we explain the math behind it so you can trust the result.
What you will find here
- Calculators: mortgage payments, BMI and percentages.
- Converters: centimeters to inches, currencies and a wide range of everyday units.
- Generators: QR codes, strong passwords and placeholder text.
- Utilities: a countdown timer, a stopwatch and a word counter.
See the full list on the All Tools page. New tools are added regularly.
How the tools work
The calculations run in your own browser. Numbers and text you type into a tool are not uploaded to our server. The currency converter is the one exception in spirit: it downloads a public table of exchange rates, but it does not send your amounts anywhere. Each tool page includes an explanation of the formula, a worked example and answers to common questions.
How the site is funded
Craig's Tool Box is free to use. We display advertising to cover hosting and development. Ads are clearly separated from the tools and are never mixed into your results. Read more in our Privacy Policy.
A note on accuracy
We test our calculators carefully, but results are estimates for general information. They are not financial, medical or professional advice. If a decision matters, check the numbers with a qualified professional.
Get in touch
Found a mistake, or have an idea for a tool you would like to see? Please use the contact page. We read every message.