FinCalculator API

Free, public, edge-cached financial calculation endpoints for India. JSON responses, CORS open, no auth required. Built on the same engine that powers fincalculator.in — so the numbers you see here are the numbers your users see.

Quick start

Every endpoint is a plain GET with query params. Try one in your terminal:

curl 'https://fincalculator.in/api/v1/sip?investment=10000&interest=12&years=10'

Limits & caching

Responses are cached for 24 hours at the edge — same input returns instantly.
No rate limit today. We'll publish one before adding any.
CORS: Access-Control-Allow-Origin: *
Versioned at /api/v1/ — breaking changes will land at /v2/.

Endpoints

GET/api/v1/sip

Compute SIP future value, total invested, and total returns.

Parameters

Name	Type	Required	Notes
investment	number	yes	Per-period amount in ₹
interest	number	yes	Annual % return
years	number	yes
frequency	string	no	daily \| weekly \| monthly \| quarterly \| yearly (default: monthly)

Example

curl 'https://fincalculator.in/api/v1/sip?investment=10000&interest=12&years=10&frequency=monthly'

GET/api/v1/emi

Compute loan EMI, total interest, total payment, and (optionally) yearly breakup.

Parameters

Name	Type	Required	Notes
principal	number	yes
interest	number	yes	Annual % rate
years	number	yes
breakup	boolean	no	Set to "true" to include yearly amortization

Example

curl 'https://fincalculator.in/api/v1/emi?principal=8000000&interest=8.5&years=20'

GET/api/v1/step-up-sip

Compute Step-Up SIP returns where the contribution increases by a fixed % or amount each period.

Parameters

Name	Type	Required	Notes
initialInvestment	number	yes
stepUpValue	number	yes
interest	number	yes
years	number	yes
stepUpType	string	no	percentage \| amount (default: percentage)
stepUpFrequency	string	no	monthly \| yearly (default: yearly)

Example

curl 'https://fincalculator.in/api/v1/step-up-sip?initialInvestment=10000&stepUpValue=10&interest=12&years=15'

GET/api/v1/compounding

Generic compound-growth calculation. Supports one-time principal, recurring contribution, or both. Returns final value, total invested, total interest, and the multiplier (Nx).

Parameters

Name	Type	Required	Notes
principal	number	no	One-time lump sum (default: 0)
contribution	number	no	Recurring contribution per period (default: 0). At least one of principal/contribution must be > 0.
rate	number	yes	Annual % return
years	number	yes
frequency	string	no	monthly \| quarterly \| yearly (default: monthly). Applies to both contribution and compounding.
breakdown	boolean	no	Set to "true" to include year-by-year breakdown

Example

curl 'https://fincalculator.in/api/v1/compounding?principal=100000&contribution=5000&rate=12&years=15&frequency=monthly'

GET/api/v1/hra

HRA exemption under Section 10(13A). Returns the three bounds and the resulting exempt/taxable split. Old regime only.

Parameters

Name	Type	Required	Notes
basic	number	yes	Annual basic + DA in ₹
hra	number	yes	Annual HRA received in ₹
rent	number	yes	Annual rent paid in ₹
metro	boolean	no	Set to "false" for non-metro 40% cap (default: true = metro 50%)

Example

curl 'https://fincalculator.in/api/v1/hra?basic=600000&hra=240000&rent=240000&metro=true'

GET/api/v1/gratuity

Gratuity payable under the Payment of Gratuity Act, 1972 or IT Act §10(10)(iii). Includes ₹20L tax-free cap and 5-year eligibility check.

Parameters

Name	Type	Required	Notes
basic	number	yes	Last drawn monthly basic + DA in ₹
years	number	yes	Years of continuous service
covered	boolean	no	Set to "false" if employer has <10 employees (default: true). Switches formula from 15/26 to 15/30.

Example

curl 'https://fincalculator.in/api/v1/gratuity?basic=50000&years=10&covered=true'

GET/api/v1/retirement

FIRE-style retirement target: required corpus, gap to fill, and monthly SIP needed.

Parameters

Name	Type	Required	Notes
currentAge	number	yes
retirementAge	number	yes
monthlyExpense	number	yes	Today's monthly expense in ₹
inflation	number	no	Annual inflation %, default 6
preReturn	number	no	Pre-retirement return %, default 12
withdrawalRate	number	no	Safe withdrawal rate %, default 4
currentSavings	number	no	Current investments in ₹, default 0

Example

curl 'https://fincalculator.in/api/v1/retirement?currentAge=30&retirementAge=60&monthlyExpense=50000'

GET/api/v1/home-loan-eligibility

Maximum home loan you qualify for using FOIR + reverse-EMI. Returns max EMI, eligible loan, property affordability.

Parameters

Name	Type	Required	Notes
netIncome	number	yes	Monthly in-hand income in ₹
existingEmis	number	no	Existing monthly EMIs (default: 0)
foir	number	no	% of income banks allow toward EMIs (default: 50)
rate	number	yes	Annual interest rate %
years	number	yes	Loan tenure
ownContribution	number	no	Down payment in ₹ (default: 0)

Example

curl 'https://fincalculator.in/api/v1/home-loan-eligibility?netIncome=100000&rate=8.5&years=20&ownContribution=1000000'

GET/api/v1/swp

Systematic Withdrawal Plan — how long a corpus lasts under fixed monthly withdrawals while earning returns.

Parameters

Name	Type	Required	Notes
corpus	number	yes	Starting corpus in ₹
withdrawal	number	yes	Monthly withdrawal in ₹
rate	number	yes	Annual return % on remaining corpus
years	number	yes	Planning horizon

Example

curl 'https://fincalculator.in/api/v1/swp?corpus=10000000&withdrawal=50000&rate=8&years=25'

GET/api/v1/cagr

Compound Annual Growth Rate. Returns CAGR %, absolute return %, and absolute gain in ₹.

Parameters

Name	Type	Required	Notes
initial	number	yes	Starting investment value in ₹
final	number	yes	Final investment value in ₹
years	number	yes	Holding period

Example

curl 'https://fincalculator.in/api/v1/cagr?initial=100000&final=250000&years=8'

GET/api/v1/inflation

Future cost of today's amount and present value of a future amount, given an inflation rate.

Parameters

Name	Type	Required	Notes
amount	number	yes	Amount in ₹
rate	number	yes	Annual inflation %
years	number	yes

Example

curl 'https://fincalculator.in/api/v1/inflation?amount=100000&rate=6&years=20'

GET/api/v1/simple-interest

Flat-rate simple interest. SI = P × r × t / 100. Returns interest, total amount, and yearly breakdown.

Parameters

Name	Type	Required	Notes
principal	number	yes	Principal in ₹
rate	number	yes	Annual rate %
years	number	yes

Example

curl 'https://fincalculator.in/api/v1/simple-interest?principal=100000&rate=8&years=5'

GET/api/v1/loan-offset

Interest-free home loan strategy: solve for the parallel SIP that offsets total loan interest. Two modes — total (SIP corpus offsets interest) and returns (SIP returns alone offset interest).

Parameters

Name	Type	Required	Notes
principal	number	yes	Loan amount in ₹
loanRate	number	yes	Loan annual interest rate %
years	number	yes	Loan tenure (also SIP tenure)
expectedReturn	number	yes	Expected annual return on parallel SIP %
mode	string	no	total \| returns (default: total)

Example

curl 'https://fincalculator.in/api/v1/loan-offset?principal=5000000&loanRate=8.5&years=20&expectedReturn=12&mode=total'

GET/api/v1/income-tax

Compute Indian income tax under old or new regime, including 87A rebate, surcharge with marginal relief, and 4% cess.

Parameters

Name	Type	Required	Notes
grossIncome	number	yes	Annual gross income in ₹
regime	string	no	old \| new-2024-25 \| new-2025-26 \| new-2026-27 (default: new-2026-27)
applyStandardDeduction	boolean	no	Set to "false" to skip standard deduction (default: true)

Example

curl 'https://fincalculator.in/api/v1/income-tax?grossIncome=1500000&regime=new-2026-27'

Using this in production?

We'd love to hear about it. Drop us a note via /contact— we'll keep you posted on schema changes and new endpoints.