Treasury Dept — Free US Treasury Interest Rates API (No Key)

TL;DR

The US Treasury's FiscalData API provides programmatic access to official Treasury financial data including average interest rates on Treasury securities, national debt, federal tax revenue, government spending, and more. The example endpoint returns the average interest rate on the US federal debt — a key economic indicator. All data is authoritative US government information updated regularly, with historical records spanning decades. No API key required for basic queries.

Quick start: https://api.fiscaldata.treasury.gov/services/api/fiscal_service/v2/accounting/od/avg_interest_rates

No API key needed — just make a request!

How to Use This API

1. Average Interest Rates

https://api.fiscaldata.treasury.gov/services/api/fiscal_service/v2/accounting/od/avg_interest_rates

2. Filter by Date Range

https://api.fiscaldata.treasury.gov/services/api/fiscal_service/v2/accounting/od/avg_interest_rates?filter=record_date:gte:2024-01-01

3. Get National Debt

https://api.fiscaldata.treasury.gov/services/api/fiscal_service/v2/accounting/od/debt_to_penny

4. JavaScript — Fetch Interest Rates

fetch('https://api.fiscaldata.treasury.gov/services/api/fiscal_service/v2/accounting/od/avg_interest_rates?page[size]=5')
  .then(r => r.json())
  .then(d => {
    d.data.forEach(row => {
      console.log(row.record_date, '—', row.avg_interest_rate_amt, '%');
    });
  });

5. Python — Rate History

import requests

resp = requests.get(
    'https://api.fiscaldata.treasury.gov/services/api/fiscal_service/v2/accounting/od/avg_interest_rates',
    params={'page[size]': 30, 'sort': '-record_date'}
)
for row in resp.json()['data']:
    print(f"{row['record_date']}: {row['avg_interest_rate_amt']}%")

Try it: https://api.fiscaldata.treasury.gov/services/api/fiscal_service/v2/accounting/od/avg_interest_rates?page[size]=3

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API Details

API URL: https://api.fiscaldata.treasury.gov/services/api/fiscal_service/v2
Documentation: fiscaldata.treasury.gov
Category: Finance
Authentication: Not Required
Geographic Coverage: USA

Frequently Asked Questions

Do I need an API key?: No. The Treasury FiscalData API is a free public government service with no authentication required.
What data endpoints are available?: Over 150 endpoints covering average interest rates, debt to the penny, tax revenues, government spending, Treasury securities, savings bonds rates, and more.
How do I filter and sort results?: Use filter=field:operator:value (operators: gte, lte, eq, neq, like) and sort=-field (descending) or sort=field (ascending). Pagination via page[size] and page[number].
What date format is used?: All dates use ISO 8601 format (YYYY-MM-DD) in the record_date field.
Can I get data in CSV format?: Yes, add &format=csv to any endpoint for CSV output. JSON is the default format.
How frequently is the data updated?: Update frequency varies by endpoint. Interest rates and debt data are typically updated daily on business days.

What You Can Build

US national debt tracker with historical trend chart
Treasury bond interest rate dashboard
Federal budget analysis and visualization tool
Tax revenue calendar showing government cash flows
Government spending breakdown by category