Guides

How to Convert Centimetres to Inches

Divide centimetres by 2.54. That factor is the definition of the international inch, not a rounded classroom shortcut, so the reverse conversion lands on the same length.

Kilograms and Pounds Explained

One international pound is exactly 0.45359237 kilograms. Body-weight scales, luggage tags and gym plates use that pound — not the troy pound used for precious metals.

Celsius vs Fahrenheit

Fahrenheit and Celsius are linear scales with different zeros and degree sizes. Convert with F = C × 9/5 + 32. They meet at −40. Oven knobs often round the result.

How Percentages Work

A percentage is a part compared with a whole out of 100. The formula changes with the sentence: percent of, what percent, or what total. Percent change between two totals is a different calculation.

Markup Versus Margin

Markup adds a percent of cost onto the cost. Margin is that same profit divided by the selling price. The two percents match only at zero and are never interchangeable on a quote.

How the Pythagorean Theorem Works

On a right triangle, the square of the hypotenuse equals the sum of the squares of the two legs. That identity finds a missing side. It does not apply to an acute or obtuse triangle unless you already know the right angle.

Mean, Median and Mode

The mean follows every value. The median is the middle after sorting. Mode is whatever appears most often. A long tail can make the mean a poor stand-in for “typical.”

How to Count Days Between Dates

Elapsed days count midnights between two dates. The same day is 0; neighbouring days are 1. Add one only if you need an inclusive count of both dates on the calendar.

How Electricity Cost Is Calculated

Cost for a session is kilowatt-hours times the unit price. Kilowatt-hours are kilowatts times hours. The nameplate is often a maximum, and the bill also has standing charges this identity ignores.

Nordic Electricity Bills and the kWh Rate

A Swedish electricity bill is not one price times kilowatt-hours. Retail energy, the local grid’s per-kWh fee and energy tax are separate lines. The fixed grid subscription does not belong in a session cost.

What BMI Measures

Body mass index is weight divided by height squared. The bands on this site are the WHO adult cut-offs. The number is a screening ratio, not body fat and not a diagnosis.

L/100 km and MPG

Litres per 100 km and miles per gallon are inverses. A US gallon and an imperial gallon are different sizes, so the same MPG number is not the same consumption. Trip cost multiplies by a price you type.

How to Create a QR Code

Encode the data you want a phone to read, download a file, scan it once yourself, then print or share that file. The pattern is the data — it does not call a server later unless you encoded a URL that does.

How to Create a Wi-Fi QR Code

A Wi-Fi QR code stores the network name, security type and password in a standard WIFI: payload. Scanning it lets a phone join without typing the password. It is a credential slip, not a live login to your router.

Do QR Codes Expire?

A static QR code does not expire. The pattern still decodes to the same characters years later. What fails is whatever those characters point at — a taken-down page, a changed Wi-Fi password, or a short link whose host cancelled the redirect.

Static vs Dynamic QR Codes

A static QR code stores the payload in the image. A dynamic QR code usually stores a short URL that redirects to the real destination so you can change the target later. MultiConvers only creates static codes.

QR Code PNG vs SVG

Download PNG when you need a ready-made pixel image at a known size. Download SVG when the same code must stay sharp on a poster or in a design file. The format does not change what the code encodes.

How to Create a Strong Password

Use a unique, randomly generated password for each site, store it in a password manager, and prefer length over a clever substitution on a short word.

How Long Should a Password Be?

For a random generated password, 16 characters is a practical default. Longer is stronger if a manager stores it. Site minimums of 8 characters are a floor, not a target.

Password Length vs Complexity

On a random password, adding characters usually beats adding a punctuation rule to a short string. Complexity rules still help when they stop you from using a dictionary word.

How to Format JSON

Formatting JSON means parsing it, then reprinting the same value with consistent indentation. Invalid text cannot be formatted — fix the syntax first.

How to Validate JSON

Valid JSON is text that JSON.parse accepts. Validation does not pretty-print or minify; it only reports whether the document is legal JSON.

JSON Pretty Print

Pretty-print reprints valid JSON with indentation so a person can read it. Minify reprints the same value as one line. Neither changes what the document means.

What Is Base64?

Base64 is a way to write binary data using 64 ASCII characters. It is encoding, not encryption. Anyone who sees the string can decode it.

How to Encode Base64

Convert text to UTF-8 bytes, then to Base64. The result is longer ASCII, not a secret. Unicode and emoji need the UTF-8 step or they will be corrupted.

How to Decode Base64

Decoding reverses Base64 back to bytes, then to text with UTF-8. Invalid characters should fail loudly. Success does not mean the original message was secret.

What Is URL Encoding?

URL encoding (percent-encoding) replaces characters that are unsafe in a URL with % and two hex digits. A space becomes %20. It keeps a query value from being read as another parameter.