Jonathan S. Kellman
Music and practical tools — from a guy who never stopped teaching
Who Is Jonathan Kellman?
Jonathan Kellman is a musician, educator, and tool-builder with three decades of teaching experience. Also known by his full name, Jonathan S. Kellman, he started on trumpet at age 10 and has since picked up more than 20 instruments, saxophone chief among them. He brings that same lifelong teaching instinct to everything he shares here, whether it’s music or the everyday tools that make life a little easier.
Jonathan Kellman now spends his time building practical calculators and tools and sharing music resources for fellow musicians and lifelong learners.
What Does Jonathan Kellman Do Today?
Today, Jonathan Kellman (Jonathan S. Kellman) works as a tool-builder and educator. He builds practical calculators like the BMI Calculator, Age Calculator, and Loan & Interest Calculator, along with music tools such as the Metronome and Capo Position Finder. Here’s what he’s put together so far:
Music Tools
Calculators and references built by Jonathan Kellman, a saxophone and trumpet player, for fellow musicians.
General Tools
Everyday calculators and converters, put together by Jonathan for everyday tasks.
How the Tools Are Built
Every calculator on this site is meant to do one job clearly. Each tool page explains the formula behind the result, walks through a worked example, and answers common questions, so you can see how the answer is reached rather than just trusting a number. Most calculators run right in your browser, and none of them need an account.
The music tools cover tuning, tempo, chords, and practice planning, drawing on decades of teaching and playing. The general tools cover money, dates, health numbers, and everyday conversions. Results are estimates for planning and learning, and they are not financial, medical, or legal advice.
Where to Start
- Tuning or practicing? Try the Music Tools, such as the Note Frequency Converter and the Practice Tempo Ramp-Up Calculator.
- Planning money or dates? Try the General Tools, such as the Loan & Interest Calculator and the Currency Converter.
- Spotted a mistake or have an idea for a new tool? Use the Contact page.