---
title: "Free public API"
description: "Every number on this page comes from an open, documented JSON API. Use it in spreadsheets, apps and AI tools."
url: "https://valuethen.com/api/"
language: "en"
site: "ValueThen"
publisher: "Rising Throne"
updated: "2026-09-02"
license: "Data: World Bank CC BY 4.0, ECB, FRED"
---

# Free public API

Every number on this page comes from an open, documented JSON API. Use it in spreadsheets, apps and AI tools.
# Free public API

Every number on this page comes from an open, documented JSON API. Use it in spreadsheets, apps and AI tools.

```
GET https://api.valuethen.com/v1/convert?amount=100&from=USD&to=EUR&fromYear=2000&toYear=2024
```

-   `/v1/convert` · `/v1/inflate` · `/v1/series/{currency}` · `/v1/coverage`

[OpenAPI reference](https://api.valuethen.com/docs)[OpenAPI spec](https://api.valuethen.com/openapi.json)

## Use this page programmatically

The same figure from the free API, no key required:

```bash
curl "https://api.valuethen.com/v1/convert?amount=100&from=USD&to=EUR&fromYear=1970&toYear=2026"
```

```json
{ "result": 777.71, "method": "cpi-then-fx", "sources": ["World Bank FP.CPI.TOTL, 2010=100"] }
```

---

Data sources: World Bank FP.CPI.TOTL, ECB HICP and reference rates, FRED CPI-U.
Free JSON API: https://api.valuethen.com/openapi.json · Agent guide: https://valuethen.com/llms.txt · MCP: https://api.valuethen.com/mcp