# Sizewise Rate Counter

> Turn “so much per year” into per second, project it, and embed a live counter. Converts a rate between seconds, minutes, hours, days, weeks, months and years, projects it over time, finds when it reaches a target and writes a small self-contained HTML counter (“since you opened this page …”) for your own site.

Part of usefulweb.app (https://usefulweb.app/). Part of [Sizewise](https://sizewise.usefulweb.app/) (ownerApp: sizewise). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://sizewiseratecounter.usefulweb.app/ (interactive tool at https://sizewiseratecounter.usefulweb.app/tool)
- JSON API: POST https://sizewiseratecounter.usefulweb.app/api/v1/calculate with a JSON object of inputs (schema: https://sizewiseratecounter.usefulweb.app/api/v1/tool)
- OpenAPI: https://sizewiseratecounter.usefulweb.app/openapi.json
- MCP (Streamable HTTP): https://sizewiseratecounter.usefulweb.app/mcp - tool `sizewise_rate_counter`

## Inputs
- label (text): What is counted
- amount (number): Amount
- per (select): Per
- unit (text): Unit of the amount
- elapsedSeconds (number): Elapsed time
- target (number): Target (optional)
- decimals (integer): Decimals in the counter

## Method
- Rate per second = amount ÷ the length of the chosen period: minute 60 s, hour 3 600 s, day 86 400 s, week 604 800 s, year 365.25 days (Julian year), month one twelfth of that.
- Projections and the time to a target are rate × time and target ÷ rate; nothing compounds.
- The embed is plain HTML with a 6-line script: it counts from the moment the page opened in the visitor’s browser, sends nothing anywhere and slows to one update per second for people who prefer reduced motion.

## Limits
- A constant rate is a simplification: real rates (spending, births, traffic) change through the day and the year.