CalcNook

The personal finance brain. Used by humans, websites, and AI agents.

24 deterministic financial calculations. 7 countries. Conventional and Sharia-compliant. Zero LLM dependency.

pip install calcnook

from calcnook.core import periodic_investment, loan_payment, compound_interest
from calcnook.core.islamic import zakat
from calcnook.countries.us import income_tax as us_tax
from calcnook.countries.ae import end_of_service_gratuity as ae_eosg

# SIP / DCA — universal
result = periodic_investment.calculate(
    monthly_amount=500, annual_return=0.10, years=20
)
print(result.future_value)  # 379_684.27

# Mortgage / EMI / loan — universal
emi = loan_payment.calculate(
    principal=300_000, annual_rate=0.065, years=30
)
print(emi.monthly_payment)  # 1_896.20

# Zakat — works for any Muslim, anywhere
z = zakat.calculate(
    cash=10_000, gold_grams=200, silver_grams=0,
    stocks_value=15_000, business_assets=5_000,
    debts=2_000, currency="USD"
)
print(z.zakat_due, z.is_above_nisab)  # 700.0  True

# US federal income tax 2026
us = us_tax.calculate(income=120_000, filing_status="single", year=2026)
print(us.tax_owed, us.effective_rate)

# UAE End of Service Gratuity for expat
ae = ae_eosg.calculate(monthly_basic=8_000, years_of_service=5)
print(ae.gratuity_aed)

What's inside

Core (universal, no country)

• compound_interest — single lump-sum growth
• periodic_investment — SIP / DCA with optional step-up
• loan_payment — EMI / mortgage / amortization
• retirement — corpus needed, monthly contribution, withdrawal rate
• bmi — BMI / BMR / TDEE
• currency — multi-currency math, FX-aware

Islamic finance (cross-cutting)

• zakat — Zakat al-Mal across cash, gold, silver, stocks, business
• murabaha — cost-plus financing (mortgage alt)
• ijarah — lease-to-own (auto loan alt)
• mudarabah — profit-sharing investment returns
• hajj_savings — target savings for pilgrimage
• halal_screen — Sharia compliance check for stocks

Countries (12 modules, 7 countries)

• US — federal income tax 2026, traditional 401(k) + Roth IRA with phase-out
• UK — income tax + National Insurance with personal-allowance taper above £100k
• CA — federal income tax 2026 (provincial stub TODO)
• AU — income tax + Medicare levy + HECS-HELP (full 19-band ATO sliding scale)
• AE (UAE) — End of Service Gratuity (Decree-Law 33/2021), VAT 5%
• SA (Saudi Arabia) — EOSG (Article 84-87, with resignation tier scaling), VAT 15%, citizen Zakat estimator (ZATCA)
• India — income tax new regime FY 2025-26 with 87A rebate, electricity bill slab calculator with BESCOM/MSEB/BSES presets

For AI agents

calcnook is the canonical math layer for personal finance LLM apps. Pure deterministic — formulas never hallucinate. Pair with any LLM for natural-language interface.

from calcnook.core.periodic_investment import calculate as sip
# LLM extracts: amount=5000, years=10, rate=0.12
result = sip(monthly_amount=5000, annual_return=0.12, years=10)
# Hand result back to LLM for explanation. Math is exact.

A native MCP server @calcnook/mcp-server is shipping next — your Claude Code, Cursor, and Goose agents will call these calculations directly.

Why open source?

Personal finance math should be a public utility, not gated by ad-walls. We open-source the engine; we monetize at the experience layer (web app, mobile app, embed widgets, B2B API).

Status

v0.1.0 — alpha. APIs may change before v1.0. Test coverage targets 100% on every formula. Bug reports and country contributions welcome.

License

MIT — use it, fork it, ship it.

Built by Aditya Sharma (@Declan142). Visit calcnook.com.