Who I am and why I built this
I'm a software developer with a background in financial services technology — primarily the insurance domain, the corner of fintech where a wrong number on a screen has real consequences for real families. Years of building and testing systems where premiums, sums assured, and payouts had to be correct to the rupee shaped how I approach every tool on this site: the formula comes first, the interface second.
calculox exists because of a frustration most Indians will recognise. When I needed to check an EMI or compare tax regimes, every calculator I found either used outdated slabs, ignored Indian-specific rules like Section 87A or ICMR BMI cutoffs, broke on mobile, or buried the result under a wall of ads. So I built all 14 calculators from scratch — focused, mobile-first, and free.
I built the platform in four months, and I'd frame that timeline honestly: it was possible because I spent it obsessively on a narrow goal — validating every formula against official RBI, Finance Act, SEBI, and GST Council sources — rather than on features nobody needs. Roughly 90% of my time on this site goes into verifying accuracy and keeping rules current; 10% goes into writing. This is not a side project I poke at on weekends — it is my primary focus.
Tools, not financial advice
I am a technologist, not a Chartered Accountant, SEBI-registered Investment Advisor, or CFP. I build tools, not financial advice. calculox provides calculation tools for educational and planning purposes only. For decisions specific to your situation, please consult a qualified CA or SEBI-registered advisor. Every calculator page carries this disclaimer, and our Terms of Service spell it out in full.
How the platform is built
- Modern, typed stack: Next.js and React with TypeScript in strict mode. Financial math runs on Decimal.js with 28-digit precision — never floating-point shortcuts — and every input is validated with Zod schemas before it reaches a formula.
- Algorithm-by-algorithm validation:each of the 14 calculation engines is a separate, independently testable module, and each one's output is cross-checked against its official source and against bank calculators (SBI, HDFC, ICICI) before it ships.
- Privacy-first architecture:all calculations run entirely in your browser. Your salary, loan amount, or weight is never sent to a server, never stored, never logged. You can verify this yourself in your browser's network tab — no data leaves the page when you calculate.
- Open to scrutiny: my work is public on GitHub, and code review of any calculation engine is available on request — email me and I'll walk you through the implementation.
How every formula is verified
Every calculator's formula is traced to a primary official source, and I re-test outputs against those sources monthly — plus immediately whenever a Budget, RBI circular, or GST Council meeting changes the rules. This is what "verified formulas" means on this site:
Reserve Bank of India (RBI)
EMI reducing-balance formula, FD quarterly compounding methodology, RD calculations, and lending rate guidelines.
Finance Act 2025-26
Income tax slabs, rebate under Section 87A, deductions (80C, 80D, 80CCD), standard deduction, and cess rates.
GST Council Notifications
GST rates (0%, 5%, 12%, 18%, 28%), CGST/SGST/IGST split, and HSN-based rate categories.
SEBI & AMFI Standards
SIP future-value methodology, CAGR disclosure norms, and mutual fund return projection conventions.
WHO & ICMR BMI Classification
Body Mass Index ranges per WHO guidelines plus the stricter Asian cutoffs adopted by ICMR for Indian populations.
The full process — sources, links, and last-verified dates for each calculator — is documented on the Verification Methodology page.
My commitment to accuracy
- Rules change, the site follows: when a Union Budget revises tax slabs or the GST Council moves a rate, updating the affected calculator is the first thing I do — the FY 2025-26 slabs, ₹75,000 standard deduction, and Section 87A rebate on this site reflect the current Finance Act.
- Found an error? Email supportcalculox@gmail.com. Correction reports jump the queue — I aim to investigate within 24 hours, because a calculator that's wrong is worse than no calculator at all.
- Honest limits:results are estimates built on documented assumptions. Where a calculator has a known blind spot — market returns aren't guaranteed, banks round EMIs, BMI can't see muscle mass — the page says so plainly instead of hiding it.
What I built
- EMI Calculator
- SIP Calculator
- FD Calculator
- RD Calculator
- Income Tax Calculator
- GST Calculator
- BMI Calculator
- Percentage Calculator
- CAGR Calculator
- Simple Interest Calculator
- Retirement Calculator
- Home Loan vs Rent Calculator
- Profit Margin Calculator
- Scientific Calculator