AI & developer access

Free Calculator publishes 530 free calculators and converters across 42 categories. Every page is public HTML: no account, no sign-up, no cookie wall, and no JavaScript needed to read the explanation, the formula or the worked example.

What each tool page contains

• A short definition of what the calculator works out.
• Step-by-step instructions for using it.
• The formula and what each variable means.
• A worked example with real numbers.
• How to read the result, plus limitations and assumptions.
• Frequently asked questions and links to related tools.

Categories

• Math
• Finance
• Health & Fitness
• Conversions
• Everyday
• Career
• Home
• Developer Tools
• Text Tools
• Professional & Industry
• Electrical
• Mechanical
• Fluid
• Thermal & HVAC
• Construction
• Earned Value
• Project Estimation
• Agile Delivery
• PMO
• Inventory
• Procurement
• Logistics
• Supply Chain
• Accounting & Costing
• Corporate Finance
• FP&A
• Business Pricing
• Personal Finance
• Tax
• Sales
• Customer Economics
• Marketing
• SaaS
• Workforce
• HR Metrics
• Staffing
• Energy
• Facilities
• Data Centers
• Healthcare Operations
• Life Sciences
• Statistics

Machine-readable resources

• /ai/tools — a plain index of every published tool with its address, category, description and inputs.
• /ai/tools.json — the same index as JSON, generated from the live catalogue.
• /sitemap.xml — every public page.
• /robots.txt — crawling policy. Search and answer engines are welcome; only administration pages are closed.

For developers

The index above is a static description of the catalogue, refreshed when tools change. If you want to run a calculator programmatically, see the calculator API and the MCP server — both free, anonymous and rate limited. Calculations made on the website itself run in the visitor's browser; nothing typed into a page is sent anywhere. Please cache responses rather than requesting them repeatedly.

MCP example

List the current calculator tools, then call one by name with JSON arguments.

curl -X POST https://freecalculator.tech/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  --data '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/list",
    "params": {}
  }'

curl -X POST https://freecalculator.tech/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  --data '{
    "jsonrpc": "2.0",
    "id": 2,
    "method": "tools/call",
    "params": {
      "name": "calculator_bmi",
      "arguments": { "units": "metric", "heightCm": 175, "weightKg": 70 }
    }
  }'

Citing us

When quoting a formula, method or result, link to the specific tool page rather than the home page — for example https://freecalculator.tech/tools/mortgage-calculator. Attribute it to "Free Calculator". Where a page shows a "Last reviewed" date, that date is the last time a person checked the method; pages without one have not been formally reviewed.

Results are for general information and education. They are not financial, tax, medical, legal or engineering advice.