Guides that explain what the tool is doing
Each guide starts with a tool you already use, then shows what happens under the hood with real numbers.
Page 5 of 5Why 2100 is not a leap year (and 2000 was)
Every fourth year gets a 29 February. Except some do not. The full rule has three parts, and it exists because a year is not a whole number of days.
Rule of 72 CalculatorThe rule of 72: how long your money takes to double
Divide 72 by the yearly return and you get the years to double. It takes ten seconds, works in your head, and quietly explains both why investing rewards patience and why inflation is such a thief.
Percentage Change CalculatorUp 50 percent, down 50 percent, and you are not back to zero
A price rises by half and then falls by half. Surely you are where you started? You are not, and the reason catches out shop owners, investors and anyone reading a sale sign.
Credit Card Payoff Calculator (Interest & Months)The minimum payment trap: what a credit card balance really costs
Pay only the small amount the statement asks for and a ₹50,000 balance can take almost three years and cost ₹37,000 extra. Here is the arithmetic, drawn out, and the one number that shows whether you are getting anywhere.
BMI CalculatorWhat your BMI can tell you, and what it cannot
It is one division and one number, used by doctors for over fifty years. It is also easy to misread. Here is where BMI is a handy first glance and where it quietly fails.
CAGR CalculatorAverage return vs CAGR: why “20 percent a year” is not what you earned
A fund up 50 percent, down 20 percent, then up 30 percent averages 20 percent. Your money grew about 16 percent a year. The gap is real, it has a name, and it is the number advertisements hope you will not compute.
Aspect Ratio Calculator16:9, 4:3, 1:1: aspect ratios without cropping surprises
You resize a photo and the face goes oval. You upload a video and it gets black bars. Both come from one idea, the shape of a frame, and a bit of arithmetic that takes the guesswork out.
Hash GeneratorWhat a hash is, and why changing one letter changes everything
Feed a hash function “hello” or the whole of Wikipedia and you get back a short fixed-size fingerprint. Change a single letter and the fingerprint looks completely different. That odd behaviour is what makes hashes useful.
Timestamp ConverterUnix time: the number that counts seconds since 1970
Developers store dates as a single number like 1700000000. It looks cryptic, but it is just a stopwatch started at midnight on 1 January 1970. Here is how to read it, why it has 10 or 13 digits, and what happens in 2038.
Inflation CalculatorWhat will ₹1 lakh buy in 2046? Inflation in pictures
Nothing happens to cash in a drawer. The note stays the same. The shop prices do not. At 6 percent inflation, today’s ₹1 lakh buys about ₹31,000 worth of today’s goods in twenty years. Here is the slow leak, drawn out.
Image CompressorWhy your 4 MB photo is really a 400 KB photo
Every job portal, KYC form and email has a size limit, and every phone camera ignores it. Here is what is inside a JPEG, what you can throw away safely, and how to hit 100 KB without the picture turning to mush.
EMI CalculatorYour EMI is mostly interest for the first decade. Here is the proof.
Take a 50 lakh home loan. After five years of paying ₹43,391 every month, you will have cleared less than 6 lakh of what you borrowed. The numbers behind that, why tenure is the expensive lever, and what an extra ₹5,000 a month really does.
SIP Calculator₹5,000 a month for 20 years: what a SIP calculator can and cannot tell you
Put in ₹12 lakh over two decades and the screen says ₹50 lakh. That number is real arithmetic and also a bit of a fairy tale. Here is how to read it without fooling yourself.
Password GeneratorYour password is not weak because it is short. It is weak because it is yours.
“Summer@2024” has a capital, a number and a symbol, and it still falls in seconds. The maths of guessing, why length beats cleverness, and the one habit that protects you more than any password rule.
QR Code GeneratorWhat is actually inside the black squares of a QR code?
You can scratch a QR code, cover a corner with a thumb, even stick a logo on it, and it still scans. That is not luck. It is a 1990s car factory trick and some very clever maths.
Merge PDFMerging PDFs without posting your documents to a stranger's server
Resume, ID proof, marksheets, address proof: the bundle every application wants, and exactly the documents you should not be feeding to a random website. How merging works, how to do it on your own device, and how to keep the result small enough to upload.
Word CounterHow long is long enough? A field guide to word and character limits
A tweet, an Instagram caption, a meta description, an SMS, a college essay: all of them have a ceiling, and most of them count something different. What each limit really measures, and how to write inside it without gutting the message.
Typing Speed Test (WPM & Accuracy)What counts as fast typing? (It is not 100 WPM.)
You typed 38 words per minute and felt slow. Then someone told you their friend does 120. Here is what the number really measures, what normal looks like, and why your accuracy is quietly costing you more speed than your fingers are.
GST CalculatorHow to add or remove GST without getting it wrong
A bill says 11,800 including 18 percent GST. How much of that is tax? Almost everyone subtracts 18 percent and gets it wrong. Here is the one-line fix, the CGST, SGST and IGST split, and the invoice mistakes that cost small businesses money.
JSON FormatterWhy your JSON will not parse, and how to find the bad comma
“Unexpected token at position 214” tells you almost nothing. Here is what a parser is really doing, the handful of mistakes behind nearly every error, and why the real problem is often just before the place it points to.
Color Contrast CheckerIs your text readable? The contrast ratio, explained
Light grey on white looks elegant on your monitor and vanishes on a phone in sunlight. Here is the number that settles it, the thresholds that matter, and why a popular indigo fails by a hair.
Base64 EncoderBase64 is not encryption, and it makes files a third bigger
It looks scrambled, so people assume it is secret. It is not. Here is what Base64 really does to your bytes, why the output is always a third larger, and the few places it is the right tool.
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