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Calculation Methodology & Sources

Friendly Calculator provides browser-based estimates for learning and everyday planning. This page explains the broad methods and assumptions behind the tools so visitors can judge whether an estimate fits their situation.

Page updated: 9 November 2026. This date is the page publication date; it does not mean every calculator has received an independent professional review on that date.

How calculations are produced

Values entered in the public calculators are processed in the visitor's browser.
Each tool uses the formula and assumptions described on its calculator page or in the relevant result explanation.
Displayed values are rounded for readability. Rounding, timing conventions and provider-specific rules can cause differences from statements or official assessments.
We do not claim that outputs are certified, audited, guaranteed or a substitute for a bank, government portal, qualified accountant, financial professional or healthcare professional.
Where a rule or rate changes, the relevant official source should be checked before relying on an estimate. A page should only be marked as reviewed after its assumptions and examples have actually been rechecked.

Calculator assumptions and limitations

GST: Performs arithmetic for the rate selected by the visitor. It does not classify goods or services or decide whether CGST/SGST or IGST applies. Check the applicable classification and rate.
Loan EMI: Uses a standard reducing-balance EMI formula with a monthly rate. Fees, insurance, changing rates, irregular payments and lender-specific rounding are excluded.
Fixed deposit: Uses the selected periodic-compounding assumption. Actual bank maturity values may differ due to day-count rules, payout choice, premature closure, tax and TDS.
EPF/PF: A simplified projection based on the entered monthly contribution and constant assumed rate. It does not model every statutory wage limit, employer/employee contribution split, withdrawals, contribution timing or annual rate changes.
SIP: Illustrates a fixed monthly contribution and constant assumed return, using month-end contribution timing. Mutual fund returns are market-linked, variable and not guaranteed; fees and taxes are excluded.
Savings interest: Uses a simple daily-balance estimate on a 365-day basis. Banks may use different balance, crediting and rounding practices.
Income tax and salary TDS: Simplified estimates using the assumptions configured in the tool. They may omit special-rate income, rebates, reliefs, exemptions, deductions, surcharge edge cases, tax regime eligibility and other individual circumstances. Confirm the relevant financial/assessment year and current law.
Salary: Divides the entered monthly amount by the entered working days and hours. It is not a statutory payroll, overtime, leave or payslip calculation.
Inflation: Projects a constant annual rate compounded over the selected period. Actual inflation changes over time.
BMI: A screening calculation, not a diagnosis. Adult categories are not applied to people under 18; children and teenagers require age- and sex-specific professional interpretation.
Fuel cost: Assumes the entered mileage and fuel price remain constant throughout the trip.
Electricity bill: Uses the per-unit and fixed charges entered by the visitor. It does not fetch a live tariff or model every state/discom slab, duty, subsidy or surcharge.
Age: Computes calendar difference between the two entered dates.
Discount and profit/loss: Basic arithmetic only; shipping, tax, overheads, platform fees and other business costs are not automatically included.

Official reference sources

These are primary reference portals for checking current rules. They are not a claim that every live rate has been automatically synced into the calculators.

Central Board of Indirect Taxes and Customs (CBIC) — GST legislation, rate schedules and guidance.
Income Tax Department — tax slabs, rules, forms and official tax calculator.
Employees' Provident Fund Organisation (EPFO) — EPF scheme and member information.
Reserve Bank of India (RBI) — banking directions and deposit-related information.
Association of Mutual Funds in India (AMFI) — investor education and mutual-fund risk information.
National Savings Institute — small-savings scheme information.

Corrections and transparency

If a result appears incorrect, send the calculator name, entered sample values and expected method through the contact form. Do not include passwords, OTPs, bank credentials, government identity numbers or other sensitive information.

We do not invent qualified reviewers, professional endorsements, user counts, test results or review dates. Any future independent review will be identified only after it has genuinely taken place.

Important disclaimer

All results are estimates for general information. They are not tax, legal, accounting, lending, investment, medical or other professional advice. Mutual fund and SIP projections are not guaranteed returns. Verify important decisions with the relevant official source or a qualified professional.