kakeru · Guide
Usage guide
Place cards, connect them, see the result. That is the whole idea.
This is not a calculator you retype a formula into — it is a calculator that keeps the structure of your calculation on the board. Split the problem into cards and the moment you change one number, every total and chart downstream follows. Work through the six steps below in order.
1. Add a card
Tap "Add calculation card" on the keypad, or long-press empty canvas (right-click on desktop). Drag cards anywhere you like. The canvas is infinite: pinch (or scroll) to zoom, drag the background to pan.
2. Type a formula
Select a single card and the card edit sheet appears above the keypad.
Type expressions such as 1200 * 4 directly — the four operations plus
parentheses, exponents and percentages. Arithmetic runs on a high-precision decimal library,
so adding decimals will not drift. Give each card a name ("Flights", "Hotel") and references
to it stay readable later.
3. Connect cards
Drag the ○ handle on a card's edge onto another card. A
reference badge — a chip standing for that card's value — is inserted into
the target card's formula. Connect "Unit price" and "People" into "Subtotal" and the subtotal
permanently means unit price × people.
- Change the source and the target recalculates automatically.
- Circular references (A→B→A) are detected and reported instead of hanging.
- The connection stays visible as a line, so "where did this number come from" is answerable.
4. Visualize it
Drag a ○ handle onto empty canvas and release: a chooser offers the display cards you can create there — bar and pie charts, progress gauges, deltas, 100% stacked bars, waterfalls, scatter plots. A display card only ever reads the cards feeding it, so editing the source numbers redraws it immediately.
To draw a formula itself, use a function plot (f(x)) card. Feed its coefficients from other cards and the curve reshapes as you move them.
5. Try what-ifs with a slider
Instead of retyping a value, drop a slider card and connect it to the cards that depend on it. Drag the knob and totals and charts follow in real time — that is how you answer "what if one more person comes" or "what if the rate goes up half a point".
6. Save and share
- Saving — your work is stored in the browser automatically, and you can keep several named projects.
- Share link — "Create share link" packs the whole board into a single URL. The board lives in the URL's fragment (after #), which browsers never send to a server, so only the person you hand the link to can see its contents.
- Export — save the board as a PNG image or a JSON file. JSON can be imported back, which doubles as your backup when moving devices.
Start from a template
Rather than starting blank, open the menu and pick "Templates" for ready-made boards — trip budgets, mortgage payments, cost of living. Everything in them is editable, so replacing the numbers with yours is the fastest way in.
FAQ
Where is my data stored?
Only in your browser's local storage — there is no server, and nothing you type is uploaded. See the privacy policy for details.
Can I lose my data?
Clearing your browser's cache or cookies can remove it. Export important boards as JSON. For mistakes there is also a generational backup (menu → "Restore from a generation") that rolls the board back to an earlier state.
Does it work offline?
Once you have opened it, yes — it starts and calculates with no connection. Add it to your home screen to launch it like an app.
Is it free?
Yes, and there is no account to create. Development is funded by ads, which are kept out of the canvas itself.