Written by Jere Salmisto·Reviewed by CalcFi Editorial·Last verified:
Developer API — Coming Soon

CalcFi Developer API — coming soon

Hundreds of calculators, one API. Join the waitlist.

Request API AccessView Endpoints
100s
Calculators
REST
JSON API
<50ms
Response Time

Authentication

All API requests require a Bearer token in the Authorization header. API keys are issued per-application and available through your dashboard.

RESTJSONHTTPSBearer Auth
# Base URL
https://api.calcfi.app
# Authentication
Authorization: Bearer YOUR_API_KEY
Content-Type: application/json

API Reference

Every endpoint accepts JSON and returns structured results.

POST
/v1/calculate/mortgage

Calculate monthly mortgage payment, total interest, and amortization schedule.

Parameters

NameTypeRequiredDescription
principalnumberrequiredLoan amount in USD
annual_ratenumberrequiredAnnual interest rate as a decimal (e.g. 0.065)
term_yearsintegerrequiredLoan term in years (e.g. 30)
include_amortizationbooleanoptionalReturn full amortization schedule

Request Body

{
"principal": 400000,
"annual_rate": 0.065,
"term_years": 30,
"include_amortization": false
}

Response

{
"monthly_payment": 2528.27,
"total_interest": 510178.20,
"total_cost": 910178.20,
"payoff_date":"2055-04-01",
"meta": {
"calculator":"mortgage",
"version":"1.0",
"computed_at":"2025-04-01T12:00:00Z"
 }
}
POST
/v1/calculate/compound-interest

Calculate compound interest growth with optional regular contributions.

Parameters

NameTypeRequiredDescription
principalnumberrequiredInitial investment amount
annual_ratenumberrequiredAnnual interest rate as a decimal
yearsintegerrequiredInvestment duration in years
monthly_contributionnumberoptionalRegular monthly contribution
compound_frequencystringoptional"monthly" |"quarterly" |"annually"

Request Body

{
"principal": 10000,
"annual_rate": 0.07,
"years": 30,
"monthly_contribution": 500,
"compound_frequency":"monthly"
}

Response

{
"final_value": 613089.34,
"total_contributions": 190000.00,
"total_interest_earned": 423089.34,
"growth_multiple": 3.23,
"yearly_breakdown": [
 {"year": 1,"value": 17283.40 },
 {"year": 5,"value": 51640.28 }
 ]
}
POST
/v1/calculate/retirement

Project retirement savings and determine required monthly contribution to reach a goal.

Parameters

NameTypeRequiredDescription
current_ageintegerrequiredCurrent age in years
retirement_ageintegerrequiredTarget retirement age
current_savingsnumberrequiredCurrent retirement savings balance
monthly_contributionnumberrequiredCurrent monthly contribution
annual_returnnumberoptionalExpected annual return (default 0.07)

Request Body

{
"current_age": 35,
"retirement_age": 65,
"current_savings": 50000,
"monthly_contribution": 1000,
"annual_return": 0.07
}

Response

{
"projected_balance": 1247892.50,
"years_to_retirement": 30,
"monthly_income_at_4pct": 4159.64,
"on_track": true,
"required_monthly_for_1m": 831.52,
"required_monthly_for_2m": 1663.04
}
GET
/v1/calculators

List all available calculators with their slugs, categories, and required parameters.

Parameters

NameTypeRequiredDescription
categorystringoptionalFilter by category (e.g."mortgage","retirement","tax")

Request

GET /v1/calculators?category=mortgage
Authorization: Bearer YOUR_API_KEY

Response

{
"calculators": [
 {
"slug":"mortgage-payment",
"name":"Mortgage Payment Calculator",
"category":"mortgage",
"endpoint":"/v1/calculate/mortgage"
 },
 {
"slug":"mortgage-affordability",
"name":"Mortgage Affordability Calculator",
"category":"mortgage",
"endpoint":"/v1/calculate/mortgage-affordability"
 }
 ],
"total": 14,
"categories": ["mortgage","retirement","investing","debt","tax","business"]
}

Error Handling

400
Bad Request
Missing or invalid parameters. Check the error.details field for specifics.
401
Unauthorized
Missing or invalid API key. Include a valid Bearer token.
404
Not Found
The requested calculator endpoint doesn't exist. Use GET /v1/calculators to list available endpoints.
429
Rate Limited
Too many requests. Default limits are 100 req/min on free tier, 1000/min on paid plans.
422
Unprocessable
Parameters are present but values are out of valid range (e.g. negative interest rate).
500
Server Error
Internal error. These are rare and monitored. Retry with exponential backoff.

Who Uses the CalcFi API

Built for developers who need accurate financial calculations without reinventing the math.

Fintech Apps

Add financial planning tools to your banking or investment app without building from scratch.

Robo-Advisors

Power retirement projections and investment calculators in automated advisory platforms.

Real Estate Platforms

Integrate mortgage, affordability, and rent-vs-buy calculations into property listings.

Mobile Apps

Fetch calculation results server-side and display them natively in iOS and Android apps.

Publisher Tools

Build custom interactive widgets that pull live calculations for editorial content.

AI Assistants

Give your LLM-powered financial assistant accurate, structured calculation capabilities.

Why CalcFi API

Sub-50ms responses
Calculations are pure math — no database lookups. Responses are fast enough for real-time UIs.
Simple REST API
Standard JSON in, JSON out. No proprietary SDKs or query languages to learn.
Always up-to-date
Tax brackets, IRS limits, and rate tables are maintained by CalcFi. You get correct results without maintaining data.
Hundreds of calculators
Mortgage, compound interest, retirement, income tax, Social Security, crypto, and more.
Structured output
Consistent, typed JSON responses. Predictable field names. Easy to integrate and parse.
Scales with you
From prototype to production. Rate limits that grow with your plan. No vendor lock-in.

Pricing (Coming Soon)

Early access users on the waitlist will receive discounted pricing.

Starter

Freeforever
  • ✓ 1,000 requests/month
  • ✓ All calculators
  • ✓ REST API access
  • ✓ Community support
Join Waitlist
Most Popular

Pro

$29/month
  • ✓ 50,000 requests/month
  • ✓ All calculators
  • ✓ Priority support
  • ✓ Webhook callbacks
  • ✓ Higher rate limits
Join Waitlist

Enterprise

Custompricing
  • ✓ Unlimited requests
  • ✓ SLA guarantee
  • ✓ Dedicated support
  • ✓ Custom calculators
  • ✓ On-premise option
Contact Us
🚀 Early Access

Request API Access

The CalcFi API is in development. Join the waitlist to get early access, shape the feature set, and receive launch pricing.

No spam. You'll only hear from us when the API launches.

FAQ

When will the API launch?

We're actively building it. Waitlist members will get early access and will be notified before public launch. Join above.

Will there be a free tier?

Yes. We plan to offer a free Starter tier with 1,000 requests/month to let developers prototype and build without upfront commitment.

Can I use the embed iframes right now?

Absolutely. While the API is in development, you can embed any CalcFi calculator on your website for free right now via the /embed page. No API key required.

Which calculators will be available?

Hundreds of CalcFi calculators. That includes mortgage, compound interest, retirement, taxes, debt payoff, crypto, business, salary, and more.

Will you build custom calculators?

Enterprise plans will include custom calculator development. If you have a specific calculation need, mention it in the waitlist form.

Citing CalcFi data

If you use CalcFi data in research, journalism, or a derivative product, please cite the dataset under CC BY 4.0:

Salmisto, J. (2026). CalcFi Open Data: 34 Free CC-BY Financial and Macro Time Series Mirrored from Primary Sources [Dataset]. Figshare. https://doi.org/10.6084/m9.figshare.32332290

The dataset is also archived with permanent identifiers at:

All entries resolve to identical content under the same Creative Commons Attribution 4.0 International licence. Attribution requested back to calcfi.app and the primary source named in each dataset's README.

Code demos and visualizations

Interactive visualizations built on the CalcFi Open Data dataset:

Want to use CalcFi right now?

While the API is in development, you can embed any calculator on your website for free today.

Get Free Embed Code