468 free online calculators covering tax, finance, health, unit conversion, math, date, everyday life, and programming. No ads, no sign-up, no popups. Every calculation runs client-side — your data never leaves your browser. Built with Next.js SSG for sub-second load times. Japanese and English bilingual support. New calculators added weekly based on user requests. From BMI and loan payments to hex converters and regex testers — if you need to calculate it, it's probably here.
I started building Keisan Tools when I needed a Japanese tax calculator and couldn't find a good free one online. One calculator turned into 10, then 50, then 468.
Every calculator:
- Loads in under 1 second (static site generation)
- Runs entirely in your browser (zero server calls)
- Has no ads, no sign-up, no premium upsell
I add about 5 new calculators every week based on requests. Recent additions: pension estimator, household budget planner, mortgage prepayment simulator.
What calculator do you wish existed but can't find online? I'll build it and tag you when it's live.
