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 2 of 5CGPA to percentage: how to convert with the 9.5 rule and why universities differ
Job forms and college applications often ask for a percentage, but your marksheet shows a CGPA. This guide covers the CBSE 9.5 multiplier, the reverse conversion, a full lookup table, why other universities use other formulas, and how to avoid a mismatch on your application.
Quadratic Equation SolverQuadratic equations explained: the formula, the discriminant and what the roots mean
Every quadratic ax² + bx + c = 0 has the same solution formula. One number inside it, the discriminant, tells you in advance whether you will get two answers, one, or none you can plot. This guide solves four examples and ends with a ball thrown into the air.
Confidence Interval Calculator (Mean)Confidence intervals explained: what 95% really means and how sample size shrinks it
A poll says 52% support a plan, give or take 3 points. A confidence interval is that 'give or take', done properly. This guide shows the formula, a worked example, how level and sample size change the width, and the common misreading of '95% confident'.
Ohm’s Law Calculator (Voltage, Current, Resistance, Power)Ohm's law explained: volts, amps, ohms and watts with worked examples
Voltage, current, resistance and power are linked by two short formulas. Learn the triangle, the twelve-formula wheel, how to size an LED resistor, why a kettle draws 8.7 amps, and how series and parallel resistors change the numbers.
Robots.txt Generatorrobots.txt explained: Allow, Disallow, wildcards and the mistakes that block your site
One small text file can tell search engines to crawl your whole site or none of it. This guide covers the four directives that matter, how crawlers pick between conflicting rules, why robots.txt is not a security tool, and the single-character slip that has taken sites out of search.
Chmod Calculatorchmod permissions explained: what 755, 644 and 777 actually mean
Every file on Linux and macOS carries nine permission bits. chmod 755 sets them in one go, but only if you can read the number. This guide decodes the digits, lists the values you will use most, explains umask and the special bits, and shows why 777 is almost never the answer.
Z-Score CalculatorZ-score explained: compare anything on one scale and spot outliers
A score of 78 in maths and 70 in science: which is the better result? A z-score answers that by counting how many standard deviations a value sits from the average. This guide covers the formula, the percentile table, the 68-95-99.7 rule, and how rare 3, 4 and 5 sigma events really are.
Loan Amortization CalculatorLoan amortization schedule explained: why early EMIs are mostly interest
On a 20-year home loan, your first EMI sends about 80% of its money to interest. This guide builds the schedule month by month, shows the exact month the balance tips the other way, and tests what extra payments really save.
Hreflang Tag Generatorhreflang tags explained: language codes, x-default and the return-link rule
If your site exists in more than one language or country version, search engines need to know which page is for whom. hreflang tags say so. This guide covers the code format, the three ways to add the tags, why every page must link back and the mistakes that make the whole set ignored.
Percent Error CalculatorPercent error: how far off is your measurement, and how it differs from percent change
You measured gravity as 9.6 m/s² and the textbook says 9.81. How wrong are you, in percent? This guide shows the one-line formula, three worked examples, how it differs from percent difference and percent change, and what size of error is acceptable.
IBAN ValidatorIBAN explained: how the mod-97 check catches typos and what each part means
An IBAN looks like a random string, but every character has a job. This guide breaks one apart, walks through the mod-97 check by hand, shows how many typing mistakes it catches and explains why a valid IBAN is not the same as a real, working account.
Sitemap XML Generatorsitemap.xml explained: what to include, the 50,000 URL limit and HTML sitemaps
A sitemap is a list of pages you want search engines to find. It does not guarantee ranking, but it helps new and deep pages get discovered. This guide covers the tags that matter, the limits, the mistakes that waste crawl time and how an HTML sitemap helps real visitors.
Waist to Hip Ratio CalculatorWaist-to-hip ratio: how to measure it and what the 0.85 and 0.90 lines mean
BMI says nothing about where your body carries weight. Waist-to-hip ratio does. This guide shows how to measure correctly, how to read the number, why the same waist can give different results and what the ratio can and cannot tell you.
Pascal’s Triangle GeneratorPascal's triangle: patterns, coin flips and the numbers behind combinations
Start with a single 1 and add two numbers to get the one below. That tiny rule builds a triangle hiding powers of 2, the Fibonacci sequence, the coefficients of (a + b)ⁿ and the odds of every coin-flip result. This guide walks through each pattern with pictures.
Linear Regression Calculator (Line of Best Fit)Linear regression: the best-fit line, slope, intercept and R² explained
Study hours against marks, ad spend against sales, temperature against ice-cream orders. Linear regression draws the one straight line that fits the points best and lets you predict the next one. This guide builds it by hand from eight data points and shows where it breaks.
Sample Size CalculatorSample size: how many people do you need to survey?
Why can a poll of 1,000 people describe a country of 100 million? This guide explains margin of error, confidence level and the 385 rule in plain words, with charts that show where adding more respondents stops being worth the cost.
Dividend Yield CalculatorDividend yield explained: the yield trap, payout ratio and the power of reinvesting
A high dividend yield looks like free money. Sometimes it is; sometimes it is a warning sign. This guide shows how yield is calculated, why it can jump without the company paying a rupee more, what payout ratio tells you and how reinvested dividends change a 20-year result.
Projectile Motion Calculator (Range, Height, Time)Projectile motion: why 45 degrees throws farthest (and when it does not)
Throw a ball, kick a football or launch a water rocket and the path is the same curve. This guide explains it with one rule, five launch angles, four planets and a few real numbers, so you can predict range, height and flight time before you throw.
Pythagorean Theorem CalculatorPythagorean theorem: the 3-4-5 trick, ladders, TV sizes and how to check a right angle
a² + b² = c² is the most useful line in school geometry. This guide shows what it really says, how carpenters use a 3-4-5 rope to square a room, why a '55-inch' TV is not 55 inches wide and how to test whether any triangle has a right angle.
Regex TesterRegex from zero: ten patterns and the trap that freezes pages
A regular expression looks like a cat walked across the keyboard. It is really a tiny language for describing text. Learn six symbols and you can check a PIN code, pull numbers out of a paragraph or tidy a messy list. Learn one warning and you will not freeze your own page.
EPF CalculatorEPF: how your provident fund grows over 30 years
A few thousand rupees leave your salary every month and you barely feel it. Thirty years later it can be a crore or more. Here is what actually goes into your EPF, how it compounds, and the one habit that quietly costs people lakhs.
One Rep Max (1RM) CalculatorOne rep max: estimate your max lift without risking it
You lifted 80 kg for five clean reps. What could you lift for one? A few well-known formulas turn a set you already did into an estimate of your max, and a percentage table tells you what to load on the bar next week. No heavy single needed.
Correlation Coefficient Calculator (Pearson r)Correlation: what r tells you, and what it never can
Ice cream sales and drownings rise together. Does ice cream cause drowning? One number, r, measures how closely two lists move together. It is easy to compute and even easier to misread. Here is how to read it properly.
Debt Payoff Calculator (Snowball vs Avalanche)Snowball or avalanche: which way to clear several debts?
Pay the smallest balance first, or the highest interest first? People argue about it online as if one answer is right. We ran the same four debts through both methods. The gap was ₹1,289. The real lesson is somewhere else.
Mortgage CalculatorHome loan: where your EMI goes in year 1 and in year 20
You pay the same EMI for twenty years, but the money inside it changes sides. In year one about four out of five rupees go to the bank's interest. By year twenty almost nothing does. Seeing that shift is the key to every smart move on a home loan.
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