DevKit: a one-file calculator library with tested formulas — now with an LLM cost calculator
I kept reaching for a quick calculator and landing on pages crowded with ads, pop-ups, and distractions. So I built the tool I wanted instead: a lean calculator site that gets out of the way.
DevKit is a one-file calculator library with 69 tools, all running client-side in your browser. The tools are organised into tabbed pages, so you can find the one you need without scrolling through a long list.
What's new: an LLM cost calculator
The newest addition is for anyone working with language models. The LLM cost calculator helps you estimate what a request will cost, and the tokens/sec simulator shows how generation speed affects timing. It's the part I reach for most when I'm planning an LLM feature and want a quick sense of cost and speed before writing code.
Verified formulas
A calculator is only useful if you can trust its answers, so the formulas in DevKit are verified with tests. That gives me a way to catch mistakes when a formula changes, instead of hoping the numbers look right.
Try it
What calculator should I add next? Let me know in the comments — I'd love to hear what you'd actually use.