Web App
renzan
Place cards, connect them, and let the calculation run through.
A new kind of calculator. You turn formulas into cards, connect them to each other, and visualize the results on the spot. "People × unit price," "rate × principal" — you build the kind of math you actually think through, all on a single board.
What you can do
- Connect calculation cards — reference one card's result from another formula; change it and everything recalculates.
- Visualize instantly — bar & pie charts, progress gauges, deltas, stacked bars, waterfalls, scatter plots.
- Function plots f(x) — type a formula to draw the curve; drive its coefficients from other cards.
- What-if with sliders — drag a value and the connected charts follow in real time.
- Save & share — share a board by URL or image, or start from a template.
Where it fits
- Money — budgets, trip costs, mortgages, investment simulations.
- Math — visualize functions, areas, and ratios.
- Science — unit math, physical quantities, correlation of experimental data.
- Life planning — long-term simulations like education funds and retirement.
About the name
renzan is the Japanese 連算 — a chained calculation. It is not decoration; it is what the app actually does:
- 連 — the chain. Connect two cards and the value flows through. Change one number upstream and every answer downstream follows it.
- 算 — the arithmetic, kept in view. Not just the answer: the working stays on the board, so you can come back and see how you got there.
- And the chain travels. A finished board goes out as a URL or an image. With no server in the middle, it goes from one person straight to another.
Privacy
There is no server behind renzan. Your data is stored only in your browser, on your device, and is never uploaded anywhere. Use it with confidence even for household budgets and personal numbers.
Running in the browser alone is renzan's own choice, not a rule codinganyway applies to everything it builds.