Guides

Plain-language walkthroughs for the tasks our tools handle. Each guide covers the built-in way to do it on Windows, Mac, iPhone and Android, the free options compared honestly, and where a browser tool is genuinely the better route.

All guides

Daily Tools

Why Is My Camera Not Working? A Layer-by-Layer Fix

Fix a camera that shows a black screen or a permission error on a laptop, iPhone or Android, and inside Teams, Zoom, Meet, FaceTime, TikTok and Snapchat.

How to Calculate Percentage of Total (Excel, Sheets, Pivot, Tableau)

Work out percentage of total by hand, in Excel, Google Sheets, a pivot table or a Tableau calculated field — with worked examples and the traps to avoid.

How Is GPA Calculated? The 4.0 Scale, Credit Weighting, and Who Recalculates It

How GPA is worked out: the 4.0 scale, credit-hour weighting, weighted versus unweighted, and why LSAC and AMCAS recalculate a different number. With examples.

What Is Prime Factorization? Definition, Methods and Worked Examples

Prime factorization written out in plain English: what it means, why it is unique, how to find it with a factor tree or ladder, plus seven worked examples.

How to Make a Meme from Any Photo (iPhone, Android and Desktop)

Make a meme from any photo on iPhone, Android or desktop — add top and bottom captions and export a PNG in your browser. No app, no upload, no account.

How to Calculate Age from a Date of Birth (Excel, Sheets and SQL)

Calculate age from a date of birth in Excel, Google Sheets and SQL: DATEDIF for exact years and months, a specific reference date, and the SQL Server fix.

Why Does White Noise Help You Sleep? The Masking Mechanism, Explained

The masking mechanism behind white noise and sleep, what the evidence does and does not support, plus white, pink and brown sound, volume and placement.

How to Use a Scientific Calculator (and Why It Answers Differently Than You Do)

Order of operations, degrees versus radians, negative bases, E notation, fractions, chemistry chains and statistics with memory keys — explained for beginners.

How to Generate a Truly Random Number (and Which Kind You Actually Need)

True randomness versus a CSPRNG versus a plain generator: why Math.random() fails for secrets, and how rejection sampling removes modulo bias.

How to Create a Strong Password That You Can Also Remember

A strong password explained with real arithmetic: entropy, why length beats symbol soup, passphrases you can remember, and what a generator will not do.

How to Increase Typing Speed, Starting With the Errors

Increase your typing speed in the order that works: accuracy first, slow deliberate practice, an even rhythm, then the characters drills forget.

What Is the Pomodoro Technique?

What the Pomodoro Technique actually is, why the 25/5 structure helps, how to adjust it for studying and deep work, and how to start your first session.

Why Do Designers Use Lorem Ipsum?

Why designers use lorem ipsum instead of real copy: what dummy text actually tests, where the scrambled Latin came from, and when it will mislead you.

How to Simplify a Fraction (Divide Top and Bottom by the Same Number)

Simplify a fraction by dividing top and bottom by their GCD. See the method for mixed numbers, division, and negatives — and when a calculator helps.

Privacy File Tools

How to Convert JPG to PDF (Windows, Mac, iPhone and Android)

Convert JPG to PDF on Windows, Mac, iPhone and Android, step by step — including a free browser method that needs no install and never uploads your photos.

How to Convert PDF to JPG (Windows, Mac, iPhone, Android and Acrobat)

Convert PDF to JPG or PNG on Windows, Mac, iPhone and Android step by step — including a free browser method that exports every page without an upload.

How to Combine PDF Files into One Document (Mac, Windows and More)

Combine PDF files into one document on Mac, Windows, and in Adobe or Bluebeam — plus a free browser method that reorders pages and never uploads your files.

How to Convert PNG to JPG (Windows, Mac, iPhone and Android)

Convert PNG to JPG on Mac, Windows, iPhone and Android, step by step, including a free browser method with no upload and what really happens to quality.

How to Compress a PDF for Email (Windows, Mac, Phone and Browser)

Compress a PDF for an email attachment on Windows, Mac, iPhone and Android. How limits work, when a smaller file comes out bigger, and a free browser route.

Why Can't I Open HEIC Files on My PC — and Six Ways to Fix It

HEIC photos from an iPhone won't open on Windows? Here's why the decoder may be missing on your PC, what HEIC actually is, and six real fixes.

How to Create a Barcode for a Product (The Number, the Symbol, and the Print)

Choose the right symbology, work out the check digit yourself once, and understand why a barcode you generate is not a product code you actually own.

How to Resize an Image Without Losing Quality (and What That Phrase Actually Means)

Resize an image without losing quality: clean resampling, avoiding double JPEG compression, picking the right format, and the truth about upscaling.

How to Add a Watermark to a PDF — and What a Watermark Actually Protects

Watermark every page of a PDF in your browser with no upload. See what a watermark really deters, why it cannot protect a file, and what does restrict access.

How to Save a Word Document as a PDF (Windows, Mac, iPad and iPhone)

Save a Word document as a PDF on Windows, Mac, iPad and iPhone, step by step — including exactly what a browser conversion changes and how to keep layout.

Cross-border Finance

How Much Money Do You Need to Retire?

Work out how much money you need to retire at 40, 45, 50, 55, 60, 62 or 65, including the 25-times rule, where it comes from, and free calculators.

Best Time to Exchange Currency: What Actually Sets What You Pay

Nobody can time the currency market. Here is what actually sets your cost abroad, and the arithmetic that compares two currency quotes in a minute.

How to Calculate EMI for a Loan (Formula, Worked Example, Excel)

Calculate loan EMI with the standard amortization formula, a fully worked example, the Excel PMT route, and why a flat-rate quote is not the same number.

SIP vs Lump Sum: Which Is Better, and How to Think About It

A lump sum wins on paper and a monthly plan survives real behaviour. Here is the honest structure: time in market, sequence risk, and what no projection sees.

How to Calculate Compound Inflation: Two Formulas and a Rate You Bring Yourself

Compound inflation is exponentiation, not addition. Here are the two formulas, the rate you must supply yourself, worked examples, and where this tool breaks.

How to Pay Off Credit Card Debt Faster

See why minimum payments keep you in debt for decades, compare the avalanche and snowball methods, and plan your payoff with three free browser calculators.

How to Calculate Mortgage Payments (The Monthly Payment Formula)

Calculate a mortgage payment with M = P × r(1+r)^n / ((1+r)^n − 1). Learn the monthly math by hand or Excel, rate systems, and what a lender's quote adds.

How to Convert Salary to Hourly (And Back Again)

Convert salary to hourly by dividing annual pay by hours per week × working weeks. See the formula, other periods, 48-weeks rule, and what it omits.

Local AI Tools

How Does OCR Work? The Pipeline, Stage by Stage

How OCR works stage by stage: how an image becomes text lines, lines become characters, why each stage fails, and how Tesseract's LSTM engine reads text.

How to Check Grammar in a Document, in the Right Order

How to check grammar in a document: the order to check in, what spellcheck misses, what a paste silently drops, and proofreading your own writing.

How to Transcribe Audio to Text for Free

Transcribe audio to text for free with no account, key, or upload. What Whisper actually does in your browser, how to get a clean transcript, and when not to.

How to Turn Text into Audio (Free, Audiobook, iPhone)

Turn text into audio for listening, export, or narration. Three routes from OS read-aloud to a neural browser tool, writing tips, and what still sounds robotic.

How Accurate Is AI Translation? What the Answer Actually Depends On

AI translation accuracy is not one number: it depends on the language pair, the text type, and how much context the system can see. Here is how to judge it.

How Does Object Detection Work?

How object detection turns an image into labelled boxes: bounding boxes, the two detector families, what a confidence score means, NMS, and failure modes.

How Does Image Recognition Work?

How image recognition works in plain terms: what a model really sees, what a confidence score means, why faces are a separate problem, and the limits.

Health Tools

How Many Calories Do You Need a Day? (Real Numbers, Goal by Goal)

How many calories do you need a day? The Mifflin-St Jeor equation gives your baseline, then targets for losing, maintaining, gaining, and breastfeeding.

How Many Steps Is a Mile? The Real Numbers for Walking, Running and Everything Between

Steps in a mile depend on your height and pace: roughly 2,213 walking for a 5 ft 9 man, 2,397 for a 5 ft 4 woman, and far fewer running. Here is the math.

What Is My Chinese Zodiac Animal? The Boundary Rule That Decides It

Find your Chinese zodiac animal from your full birth date, not your birth year. The year turns at Lunar New Year, so early birthdays get a different animal.

How to Predict a Child's Height as an Adult (Mid-Parental Method)

Estimate a child's adult height from the parents' heights with the mid-parental formula — boys +6.5 cm, girls −6.5 cm — plus a realistic ±8.5 cm range.