Luminth builds free, accurate calculators and interactive tools designed to help people make better-informed decisions about everyday tasks and activities. Every tool on this site runs entirely in your browser, no account required, no data collected, no paywalls.
We believe the best tools shouldn't be locked behind a subscription or buried inside a cluttered app. A well-designed calculator or tool, available instantly, is one that simply works.
Too many calculator and tool sites are slow, or give you a result with no explanation of how they got there. We wanted something different: tools that are fast, transparent about their formulas, and honest about what the numbers mean.
Luminth started with one calculator and a simple goal: build the most useful, most trustworthy version of each tool on the internet, and keep adding more over time.
Every Luminth calculator uses arbitrary-precision math to avoid the floating-point rounding errors that plague most browser-based tools. Results are computed on your device in real time, and nothing is sent to a server. We publish the exact formulas we use so you can verify the calculations yourself.
Luminth is built and maintained by Keegan Grovert, a developer focused on building clean, performant web experiences. If you find a bug, have a suggestion for a new tool, or just want to say hello, reach out directly.
Ready to try one of our tools?
Mortgage Calculator