The how and why behind the tools.

How is EMI calculated? Learn the EMI formula, see a worked example for a home, car and personal loan, and understand how rate and tenure change your monthly payment.

How to calculate percentage increase and decrease with a simple formula and worked examples. Learn the difference between percentage change and percentage points.

Understand mortgage principal vs interest: how amortisation splits your monthly payment, why early payments are mostly interest, and how extra payments save you money.

How is GST calculated in India? Learn the GST formula to add GST to a base price, remove GST from an inclusive price, and split tax into CGST and SGST, with worked examples.

How does a SIP work? Understand systematic investment plans, the SIP return formula, rupee-cost averaging and the power of compounding, with a clear worked example.

What is compound interest? Learn the formula A = P(1 + r/n)^(nt), how it differs from simple interest, a worked example, and the Rule of 72.

How is FD interest calculated? Learn how Indian banks use quarterly compounding, the formula M = P(1 + r/4)^(4t), and a clear worked example.

How is PPF interest calculated? Understand the Public Provident Fund annual compounding formula, the monthly-balance rule, the 15-year tenure and tax benefits, with a worked example.

Old vs new tax regime for FY 2025-26 (AY 2026-27): compare the slab rates, the standard deduction, the 12 lakh tax-free limit and a worked example to see which regime gives you lower tax.

How HRA exemption is calculated under Section 10(13A): the 3-way rule, metro vs non-metro limits, a worked example, and the documents you need to claim it under the old tax regime.

Why your take-home pay is far below your CTC: how employer PF, gratuity, your own PF, professional tax and income tax are deducted, with a full worked example for FY 2025-26.

How gratuity is calculated in India under the Payment of Gratuity Act: the 15/26 formula, the 5-year eligibility rule, how part-years are rounded, the tax-free limit, and a worked example.

How the National Pension System builds a retirement corpus from monthly contributions, why at least 40% must buy an annuity, how the monthly pension is worked out, and the tax rules - with a full worked example.

How Indian banks work out recurring deposit maturity with quarterly compounding, why the tenure runs in multiples of 3 months, how RD differs from an FD and an SIP, plus a full worked example and the tax rules.

How a one-time lumpsum investment compounds into its maturity value, the formula behind it, how lumpsum differs from an SIP, a full worked example, and the effect of time, rate and tax on your return.

Should you invest a sum all at once or spread it as a monthly SIP? A like-for-like comparison with worked numbers, why the lumpsum usually wins on paper, when an SIP wins in practice, and what to do with the cash while it waits.

How an SWP pays you a fixed amount each month while the rest of your corpus keeps growing, the month-by-month formula behind it, a full worked example, when a corpus runs dry, and how to size a withdrawal that lasts.

What compound annual growth rate (CAGR) means, the formula behind it, a full worked example, why it beats a simple average return, how it differs from total return, and where it falls short.

What return on investment (ROI) means, the simple formula behind it, a full worked example, the difference between total and annualized ROI, and the costs and blind spots the raw number leaves out.

What simple interest means, the SI = P × R × T / 100 formula explained term by term, a full worked example, how to rearrange it to find the rate, time or principal, and how it differs from compound interest.

What inflation is, the future-cost and purchasing-power formulas explained, a worked example over 10 and 25 years, why real returns matter more than headline returns, and how to plan around rising prices.

What actually counts as a word, the difference between characters with and without spaces, how reading time is estimated, the word and character limits that matter for essays, tweets and SEO, and how many words fit on a page.

The six text case formats a case converter produces - UPPERCASE, lowercase, Title Case, Sentence case, camelCase and snake_case - how each transformation works, the title-case rules it does and doesn't apply, and which case to use for headings, prose, code and file names.

What lorem ipsum is, where the half-Latin came from, why designers use placeholder text, how to generate exactly the amount you need, and when you should never use it.

A URL slug is the readable, keyword-carrying tail of a web address, like how-to-brew-coffee. Learn what a slug is, what makes a good one, how a title becomes a clean slug, why hyphens beat underscores, and whether you should ever change a slug after publishing.

How to sort a list alphabetically online, and why most sorters get it wrong: capitals sorted before lowercase, item10 before item9, accented words dumped past Z. What real dictionary order does instead.

How to remove extra spaces from text, and why your double spaces survive find-and-replace. The no-break and zero-width characters pasted from Word, PDFs and spreadsheets, explained.

How to strip HTML tags from text properly: why a regex leaves JavaScript and CSS behind, where line breaks belong, and the order entity decoding has to run in.

How to remove line breaks from text copied out of a PDF, email or website: join lines with a space or nothing, collapse leftover double spaces, and handle paragraphs, hyphens and URLs.

What is Base64 and when should you use it? Learn how Base64 encoding works, why it makes data 33% larger, why it is not encryption, and the URL-safe variant.

What is inside a JWT? Learn the three parts of a JSON Web Token - header, payload and signature - and why decoding a token is not the same as verifying it.

MD5 vs SHA-256 explained: how cryptographic hash functions work, why MD5 and SHA-1 are broken, when to use SHA-256, and why you should never hash passwords.

What is JSON? Learn JSON syntax and data types, the rules that make it valid, common errors like trailing commas, plus how to format or minify it.

What is a UUID? Learn the 128-bit UUID format, how version 4 (random) UUIDs work, why collisions are nearly impossible, and when to use them as identifiers.

What is URL encoding? Learn how percent-encoding escapes spaces and special characters in URLs, which characters are reserved, and when to encode.

How to format SQL queries: one clause per line, indented JOIN conditions, keyword casing and comma style - the conventions, with a full before and after.

Do QR codes expire? The pattern itself never does — but the redirect behind a dynamic QR code can be switched off. How to tell which kind you have, and how to make one that lasts.

What is a token in an LLM? How tokens differ from words, why the same sentence costs more in Hindi than English, which encoding each GPT model uses, and how to count tokens exactly.

How to format XML: what indentation is safe to add, why mixed content must stay on one line, when trimming a text value changes your data, what the well-formedness check catches, and when to minify instead.

How to escape a string properly: what changes per format, the ordering bug in nearly every hand-rolled escaper, the characters XML cannot hold at all, and why escaping is not a security control.

How to read a cron expression field by field, with a worked example — plus the day-of-month/day-of-week OR rule, the step that does not wrap, and what cron cannot express at all.

How to beautify and indent HTML safely. Why a line break between inline tags adds a visible space, which elements you can indent freely, and what pre, script and custom elements need.

How webhook signatures work, how to check one with HMAC-SHA256, and the four reasons a signature does not match: key encoding, algorithm, message bytes and comparison.

How HTML entities work: which characters must be encoded, when to use named, decimal or hex references, why &copy without a semicolon still renders, and how to fix double-encoded text.

How to check a downloaded file against its published SHA-256 or MD5 checksum - in the browser, on macOS, Linux and Windows - what to do when it does not match, and why a match is not proof the file is genuine.

What Base64 does to an image file, what inlining one really costs once gzip is involved, when a data URI is worth it, and why an SVG should never be Base64 at all.

Turn a JSON response into TypeScript interfaces. How optional and nullable differ, why one sample is never enough, and the fields a generator gets wrong.

What is a Unix timestamp? Learn how epoch time counts seconds from 1 January 1970 UTC, why timestamps are in UTC, seconds vs milliseconds, and the Year 2038 problem.

How to convert JSON to CSV: which JSON shapes convert cleanly, how commas and quotes are escaped per RFC 4180, what happens to nested objects, and choosing a delimiter, with a worked example.

What HEX, RGB, HSL and CMYK color codes mean, how they relate, and when to use each. Includes a worked example converting one shade across all four formats.

How to convert CSV to JSON: how the first row becomes object keys, which delimiter to pick, how quoted commas and line breaks are parsed per RFC 4180, and when to keep values as text — with a worked example.

How to convert YAML to JSON: how mappings, sequences and indentation map onto objects and arrays, how each value is typed, why unquoted numbers change, and which YAML features aren't supported - with a worked example.

How to write numbers in words: how a figure breaks into groups of three, writing an amount on a cheque, the hyphen and "and" rules, when style guides say to spell a number out, and lakh/crore vs million.

How to convert CGPA to percentage: where the CBSE 9.5 multiplier comes from, why your university's number differs, how to work out CGPA from grade points and credits, and a full worked example.

How to write the amount in words on an Indian cheque: lakh and crore grouping, writing paise, the word Only, hyphens and capitals, and the mistakes that get a cheque returned.

How to convert JSON to YAML: how objects and arrays become indented blocks, which values have to be quoted to survive, why long IDs and 1.50 get rounded by naive converters, and how multi-line text is written - with a worked example.

How to convert binary to decimal by adding place values, and decimal to binary by dividing by two. With hex, fractions, and the rounding bug that makes most online converters wrong above 9 quadrillion.

How to convert XML to JSON: how attributes and text are mapped, why a one-item list silently changes shape, what happens to namespaces, entities and mixed content, and how to keep IDs and versions exact - with a worked example.

How to convert JSON to XML: the mapping rules, a worked example, why keys get renamed, how arrays and nulls are handled, and the escaping mistakes that corrupt values.

How to write a date in Roman numerals: why a date is three numerals rather than one number, which order and separator to use, why there is no leading zero, and the mistakes that are hard to undo - with a worked example.

How to calculate age from a date of birth by hand: count years, then months, then days. A worked example, why dividing by 365 is wrong, and the two dates that have no clean answer.

How to convert Markdown to HTML: why single line breaks disappear, which features are CommonMark and which are GitHub's, what happens to raw HTML in the source, how heading anchors are generated, and when you need a whole page rather than a fragment.

How text becomes binary: characters to bytes, bytes to 8-bit groups, with worked examples both ways. Plus why accents and emoji take several bytes, and the Latin-1 bug most converters ship.

How to convert HTML to Markdown: a worked example, why some characters get a backslash, when bold has to stay as HTML, what happens to tables and tags Markdown lacks, and how to paste a web page or Google Doc straight in.

How to convert a hex color code to RGB by hand: split #RRGGBB into pairs, turn each base-16 pair into a 0-255 number, expand 3-digit shorthand, and handle 8-digit hex with alpha.

How to convert an RGB color to a hex code by hand: divide each 0-255 channel by 16, write the quotient and remainder as two hex digits, keep leading zeros, shorten to 3 digits, and add alpha.

How to merge PDF files into one online for free. Combine and reorder multiple PDFs in your browser with no upload, plus tips on splitting and compressing.

How to split a PDF online for free - extract single pages or page ranges into a new file in your browser with no upload. The steps, syntax, and related tools.

How to compress a PDF to reduce file size for free. Learn why PDFs get large, how compression works, the quality trade-off, and when it will not help.

How to convert JPG to PDF online for free. Combine JPG or PNG images into one PDF, set the page order and fit, then download - all in your browser, no upload.

How to convert PDF to JPG online for free: turn each PDF page into a high-quality JPG or PNG image right in your browser, pick the resolution, and download.

How to convert PDF to Word for free: extract the text into an editable DOCX right in your browser, choose flowing paragraphs or line-by-line, and open it in Word, Google Docs or Pages.

How to extract table data from a PDF into Excel or CSV for free: detect rows and columns automatically, preview the result, and download an XLSX or CSV - all in your browser, no upload.

How to unlock a PDF for free: remove printing, copying and editing restrictions instantly, and remove an open password by entering it once. Learn the two kinds of PDF password.

How to make a scanned PDF searchable for free with OCR. Learn what the invisible text layer is, how to tell if your PDF needs it, and what affects accuracy.

How to rotate a PDF and save the rotation for free. Why viewer rotation does not stick, what the page rotation flag does, and which angle to pick.

How to add a watermark to a PDF for free. What a watermark really is inside the file, how to pick the opacity and font size, and why it deters rather than protects.

How to add page numbers to a PDF for free: choosing the position and format, skipping a cover page, starting at a number other than 1, and setting the margin.

How to delete pages from a PDF for free: the page-range syntax, a worked example, when to use Split or Organize instead, and what changes inside the file.

How to get a PDF under a hard 100 KB, 200 KB or 500 KB upload cap - what the limit means in bytes, where a PDF actually spends them, and how to hit the number without making the document unreadable.

How to password protect a PDF for free with AES-256 encryption, in your browser. Which of the two PDF passwords actually protects a file, how to choose one, and what to do before you send it.

How to remove metadata from a PDF for free. See the author, software and dates a PDF records about you, why clearing the author box is not enough, and how to strip it in your browser.

How to extract text from a PDF without the jumbled lines. Why copy and paste breaks, how to keep paragraphs intact, and what to do when the PDF is a scan.

How to change PDF page size without losing quality. Convert a PDF to A4 or Letter, fix mixed page sizes, and understand why resizing does not shrink the file.

How to crop a PDF online: drag a box over what you want to keep, trim white margins automatically, and understand why a crop is not a redaction.

How to fill a PDF form in your browser, why some PDFs have no fields to fill, and what flattening actually does to the answers you typed.

How to pull the photos out of a PDF at full resolution, why they come out bigger than they looked, and when the original JPEG can be recovered untouched.

How to rearrange, reorder and reverse PDF pages for free: move pages with thumbnails, fix a back-to-front scan, put a duplex scan back in order, and what changes in the file.

PNG vs JPG vs WebP compared: lossy vs lossless, transparency, file size, and browser support - with a simple guide to choosing the right image format.

How to make a passport photo at home for free. Take the right photo, crop it to your country size at 300 DPI, then print or upload it and meet the rules.

How to compress an image to reduce file size while keeping it looking sharp. Learn lossy vs lossless, the right quality level, and JPG vs WebP.

How to extract text from an image with OCR. Learn how optical character recognition works, what makes it accurate, and how to turn a photo or screenshot into editable text.

How to resize an image online: change width and height, keep the aspect ratio, pick the right dimensions for web or Instagram, and why upscaling adds no detail.

How to crop a photo online: drag the selection or type exact pixels, lock a ratio like 1:1 or 16:9, pick the right crop for a profile picture, and why cropping never softens the pixels you keep.

What EXIF data records, why the GPS tag matters most, and how to read and strip metadata from a JPG, PNG or WebP in your browser without re-encoding the picture or losing any quality.

How to compress a photo to exactly 20 KB, 50 KB or 100 KB for an exam or job application form - what the limit means in bytes, why quality alone is not always enough, and how to hit the number without wrecking the picture.

How to get a photograph and signature past an SSC, IBPS, NTA or UPSC upload check - what the pixel and KB rules mean, why the minimum size is usually the harder one to meet, and how to hit both at once.

How to convert HEIC photos from an iPhone to JPG - what the format is, why Windows and web forms refuse it, how to convert a whole batch for free in your browser, and why the JPG comes out larger.

Why SVG files have no fixed size, how to pick the right pixel dimensions before converting, and how to keep transparency, sharp edges and correct text in the PNG.

How to rotate a photo 90 degrees, flip it into a mirror image, or straighten a tilted horizon - why phone photos show up sideways, which turns are lossless, and what happens to the corners.

How to watermark a photo with your name or logo - corner mark or tiled pattern, the size and opacity that work, how to mark an ID copy, and what a watermark can and cannot stop.

How to make a meme from any picture - classic top and bottom text or a caption above, the Impact font and outline that make it readable, how long a caption can be, and a worked example of the sizing.