Guides & How-To Articles

Find what percent one number is of another with the (part ÷ whole) × 100 formula, worked examples and common mistakes to avoid.

How to calculate percentage increase and decrease between two values, with worked examples and a quick comparison table of results.

Turn any score such as 40 out of 50 into a percentage in one step, with worked examples and a short table of common results.

Two similar formulas that answer different questions: when to use percentage difference and when to use percentage change, with examples.

Find the percent off and the price you actually pay, with quick shopping examples and a note on how stacked discounts really work.

The difference between a 5 percent rise and a 5 percentage point rise, why the two are not the same, and how to calculate each one.

Learn how to calculate the percentage of a number with the simple X% of Y formula, step-by-step examples, and common real-life uses.

Reverse percentage explained: find the original price before a discount using the formula original = sale price ÷ (1 − discount).

The percent error formula (measured vs actual) with worked examples, plus how to tell percent error from percentage difference.

How to calculate a tip and sales tax by percentage: quick mental math, exact formulas, and worked examples for any bill.

How to calculate your monthly mortgage payment step by step, with the formula, a $300,000 worked example, taxes and insurance.

Mortgage amortization explained: how the principal vs interest split changes over time, with a 30-year loan table and early-payoff math.

See what you actually pay on a loan — principal, interest and total cost — with worked car and personal loan examples and a cost table.

APR vs interest rate: what's the difference and which one matters, with a worked $200,000 example showing how fees raise your true rate.

Social media character limits, meta description length and SMS segment rules, with a full reference table for every major platform.

How long does it take to read 1,000 words? Reading speed (200–250 wpm) vs speaking speed (130 wpm), with a quick reference table.

URL encoding explained: how percent-encoding works, the reserved characters that break query strings, and a table of common encoded values.

JSON vs CSV when to use each: a side-by-side comparison, a conversion example, and how to turn a JSON array into clean CSV in seconds.

How to calculate percent off and sale price with the simple multiplier formula, worked examples and a table of common discounts.

How to create a URL slug from a title: lowercase, hyphen rules, stop words and SEO tips, with before-and-after examples you can copy.

What lorem ipsum is, where the dummy text comes from, why designers use it, and when placeholder text helps or hurts a project.

How to compare two texts and find the differences line by line, what added, removed and unchanged lines mean, and when to use a diff.

How much should I save each month? Work backwards from a goal, see common rules of thumb, and understand how time changes the answer.

Unix timestamp explained: what epoch time is, why it starts in 1970, seconds vs milliseconds, and how to convert it to a date.

How to convert CSV to JSON step by step: headers to keys, rows to objects, and how to handle quotes, commas and missing values.

How to randomly pick a winner fairly, why trusting a visible shuffle fails, and how to run a giveaway draw people can believe in.

Margin vs markup formula: how each is calculated, with worked examples, a comparison table and the pricing mistake to avoid.

How to convert percentages to decimals and fractions, and back, with worked examples, a conversion table and common mistakes.

How to remove line breaks and extra spaces from text, including \r\n, tabs and non-breaking spaces, with before-and-after examples.

Compound interest formula explained: A = P(1 + r/n)^(nt), worked examples, compounding frequency and the mistakes that distort returns.

How inflation affects your money: real value, purchasing power and worked examples showing what savings buy after inflation.

How to pay off credit card debt faster: how minimum payments work, extra-payment examples, and the interest you can avoid paying.

How to decode a JWT safely: header, payload and signature explained, base64url encoding and why decoding is not verification.

HTML escaping explained: why ampersands and angle brackets need entities, named vs numeric forms, and common escaping mistakes.

How random number generators work: true vs pseudo-random, uniform ranges, modulo bias, and what actually makes a draw fair.