Verification Methodology
How every calculox formula is validated — and how you can check it yourself.
How formulas are validated
Every calculator on calculox follows the same four-step process before and after it ships:
- Source first: the formula is taken from a primary official publication — an RBI direction, the Finance Act, a GST Council notification, SEBI/AMFI methodology, or WHO guidelines — never from another calculator website.
- Independent implementation:each engine is a standalone, typed module computed with 28-digit decimal precision, so rounding errors can't creep in through floating-point math.
- Cross-reference:outputs are compared against the official source's own examples and, where they exist, against public bank calculators (SBI, HDFC, ICICI) across a range of test inputs including edge cases like zero rates and leap-year day counts.
- Monthly audit: I re-run the comparison suite monthly, and immediately whenever a Union Budget, RBI circular, or GST Council meeting changes a rule that touches any calculator.
Last full audit: July 2026 — verified FY 2025-26 tax slabs, current GST rate structure, and bank calculator cross-checks after the July content update.
Official sources, by calculator
Each entry links to the primary source. All links go to official government, regulatory, or international bodies and open in a new tab.
EMI, FD, RD & Simple Interest Calculators
Reserve Bank of India — rbi.org.inReference: Reducing-balance EMI methodology used by all RBI-regulated lenders; quarterly compounding convention for bank deposits; RBI master directions on interest rates on deposits.
Cross-check: Outputs cross-checked against the public EMI and deposit calculators of SBI (sbi.co.in) and HDFC Bank (hdfcbank.com).
Last verified: July 2026
Income Tax Calculator
Income Tax Department — incometaxindia.gov.inReference: Finance Act 2025 — FY 2025-26 slab rates for both regimes, ₹75,000 standard deduction, Section 87A rebate, deduction sections 80C/80D/80CCD, HRA exemption rules, and the 4% health & education cess.
Cross-check: Results compared against the official tax calculator on the e-filing portal (incometax.gov.in).
Last verified: July 2026
GST Calculator
GST Council — gstcouncil.gov.inReference: Current GST rate slabs (0%, 5%, 12%, 18%, 28%), CGST/SGST split for intra-state supply, and IGST for inter-state supply per GST Council rate notifications (also published at gst.gov.in).
Last verified: July 2026
SIP, CAGR & Retirement Calculators
SEBI — sebi.gov.inReference: SEBI-mandated CAGR disclosure methodology for mutual fund returns; AMFI-standard SIP future-value (annuity-due) formula; NISM retirement planning framework for corpus estimation.
Last verified: July 2026
BMI Calculator
World Health Organization — who.intReference: WHO BMI classification (kg/m²) plus the lower Asian cutoffs recommended for Indian populations by ICMR — overweight at BMI 23 and obesity at 25 for South Asians.
Last verified: July 2026
Accuracy commitment
- • Results are verified against the official sources above and re-audited monthly. India-specific rules (RBI conventions, Finance Act slabs, GST rates, SEBI methodology) are applied as published by those bodies.
- • Calculations run in your browser with high-precision decimal arithmetic — the same inputs always produce the same outputs, and you can reproduce any result by hand from the formula shown on each page.
- • Small differences from a bank's final figures can still occur — lenders round EMIs, add processing fees, and post interest on their own schedules. That's a difference in fees and rounding, not in the formula.
- Spotted a discrepancy? Email supportcalculox@gmail.com with the calculator name and your inputs. Error reports are prioritised — I aim to investigate within 24 hours and publish a correction if one is needed.
Verified formulas are still estimates, not advice. calculox results are for education and planning; they are not financial, tax, or medical advice. Consult a qualified CA, SEBI-registered advisor, or doctor before major decisions. See our Terms of Service.