Guides that answer the question
23 practical guides with worked examples and real numbers — each linked to the tool that does the calculation for you.
Loans, investing & tax
EMI, SIP, PPF, income tax and salary — worked out with real numbers.
₹20 Lakh Home Loan EMI for 20 Years (8% to 10%)EMI on a ₹20 lakh home loan for 20 years is ₹17,356 at 8.5%. See EMI and total interest at 8–10%, and how much a 15-year tenure saves.25 Sept 2026 · 3 min readGST Calculation Examples: Add, Remove, CGST/SGST/IGSTHow to calculate GST with worked examples: add 18% GST to ₹10,000, remove GST from an inclusive price, and split it into CGST + SGST or IGST.25 Sept 2026 · 4 min readHome Loan EMI for ₹50 Lakh: 10 to 30 Years, 8% to 10%EMI on a ₹50 lakh home loan is ₹43,391 at 8.5% for 20 years. See EMIs and total interest for 10–30 years and 8–10% rates, and the salary you need.25 Sept 2026 · 4 min readHow SIP Returns Are Calculated (with Examples)The SIP formula explained: ₹10,000 a month for 10 years at 12% grows to about ₹23.23 lakh. See 5–25 year tables, step-up SIPs and how returns really work.25 Sept 2026 · 5 min readHow to Calculate EMI: Formula, Example and ShortcutThe EMI formula explained with a worked example: ₹10 lakh at 10% for 5 years = ₹21,247 a month. See how each EMI splits into interest and principal.25 Sept 2026 · 5 min readHow to Calculate In-Hand Salary from CTC (with Examples)CTC to in-hand salary explained step by step: ₹12 lakh CTC gives about ₹87,792 a month and ₹18 lakh gives about ₹1,21,097 in the new tax regime.25 Sept 2026 · 5 min readOld vs New Tax Regime FY 2026-27: Which Saves You More?Old vs new tax regime compared at ₹12.75, ₹15, ₹20 and ₹30 lakh salaries, with the deductions you'd need for the old regime to win.25 Sept 2026 · 6 min readPPF Maturity Calculation: How Much ₹1.5 Lakh a Year BecomesHow PPF interest is calculated and what you get at maturity: ₹1.5 lakh a year for 15 years at 7.1% grows to about ₹40.68 lakh, tax-free. Plus extension tables.25 Sept 2026 · 4 min read
GST & business
GST invoices, margins and pricing for small businesses and freelancers.
Gross Margin vs Markup: Difference & Conversion TableMarkup is profit as a % of cost; margin is profit as a % of price. A 50% markup is only a 33.3% margin. Formulas and a quick conversion table.25 Sept 2026 · 3 min readGST Invoice Format for Small Businesses (Sample Layout)A simple GST invoice format for shops, freelancers and small businesses — a sample layout with every required field, plus when to use a bill of supply instead.25 Sept 2026 · 4 min readHow to Calculate Profit Margin (with Target Price)Profit margin = profit ÷ selling price. Worked examples: cost ₹750, price ₹1,000 = 25% margin; the price for a 40% margin on ₹750 cost is ₹1,250.25 Sept 2026 · 4 min readHow to Create a GST Invoice: Mandatory Fields and StepsEverything a valid GST tax invoice must show — GSTINs, invoice number, HSN/SAC, place of supply, CGST/SGST/IGST — and how to make one as a PDF in minutes.25 Sept 2026 · 5 min read
Developer guides
JWT, JSON, Base64, hashes, UUIDs and timestamps, explained with examples.
Base64 Encoding Explained: Examples, UTF-8, Base64URLWhat Base64 is, how it works and when to use it: 'Hi!' becomes SGkh, 'Namaste' becomes TmFtYXN0ZQ==. Plus UTF-8 text, Base64URL and the 33% size cost.25 Sept 2026 · 4 min readHow to Decode a JWT: Online, JavaScript & Command LineDecode a JWT by Base64URL-decoding its header and payload — online, in JavaScript, Python or the terminal. Plus why decoding is not verifying.25 Sept 2026 · 4 min readHow to Format and Validate JSON (and Fix Common Errors)Beautify, minify and validate JSON — and fix the 6 errors that break most JSON: trailing commas, single quotes, unquoted keys, comments and more.25 Sept 2026 · 4 min readMD5 vs SHA-256: Differences and Which One to UseMD5 is fast but broken for security; SHA-256 is the safe default. See both hashes of 'hello', when MD5 is still fine, and why passwords need neither.25 Sept 2026 · 4 min readUnix Timestamp Explained: Convert Epoch Time to IST and BackA Unix timestamp counts seconds since 1 Jan 1970 UTC: 1790000000 is 21 Sep 2026, 7:43 pm IST. Convert it in JS, Python, PHP and Excel.25 Sept 2026 · 4 min readUUID v4 vs UUID v7: Which Should You Use?UUID v4 is fully random; UUID v7 starts with a timestamp, so IDs sort by creation time and keep database indexes fast. When to use each.25 Sept 2026 · 4 min readWhat Is a JWT? JSON Web Tokens Explained with an ExampleA JWT is a signed token with three parts: header, payload and signature. See a real example, what each claim means, and why a JWT is signed but not encrypted.25 Sept 2026 · 5 min read
PDF how-tos
Compress, convert and watermark PDFs — step by step.
How to Add a Watermark to a PDF (Protect Your ID Copies)Add a text watermark like 'CONFIDENTIAL' or 'For bank KYC only' to every page of a PDF — set size, colour, angle and transparency, without uploading the file.25 Sept 2026 · 3 min readHow to Compress a PDF (and Meet Upload Size Limits)Shrink a PDF for email or a government portal: pick the right compression level (72, 150 or 300 dpi), why scans are big, and what to do if it's still too large.25 Sept 2026 · 4 min readHow to Convert JPG to PDF (Phone Photos into One PDF)Turn photos of documents into one PDF: reorder pages, pick A4 or the image size, and keep the file small — on your phone or computer, without uploading.25 Sept 2026 · 3 min readHow to Convert PDF to Word (Editable DOCX)Convert a PDF to an editable Word document, keep the layout as close as possible, and know why scanned PDFs don't become editable text.25 Sept 2026 · 3 min read