About Spot Check Tools
A library of calculators and converters built for contractors, business owners, and freelancers who need a fast, correct answer.
What this site is
Spot Check Tools is a catalog of small, focused tools. Each tool computes one thing well, cites the standard or formula it follows, and shows worked examples so you can verify the math against your own situation.
Who builds it
Spot Check Tools is maintained by a small editorial team that researches the standards behind each tool, writes the explanations, and reviews the calculations. Reviewers are listed by name in the byline of every tool page along with the date the tool was last reviewed.
What we will not do
- Publish a tool we cannot defend with a citable source. If a tool depends on a regulation, we link to the regulation. If it depends on a published formula, we cite where the formula came from.
- Use AI to generate the explanations or examples. The text on every page is written and reviewed by a human.
- Ask for an email address before showing you a result. Tools work immediately, no signup, no paywall.
- Upload your files to a server. File converters run entirely in your browser via WebAssembly. The file never leaves your device.
How to reach us
Corrections, suggestions, and bug reports go through the contact page. Editorial process and review cadence are documented on the editorial standards page.