Pro Calculators and Guides
How to Simplify Ratios and Solve Proportions (Recipes, Maps and Scaling)
Reduce a ratio to its simplest form, see percentages and solve a : b = c : x to find the missing value.
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Pro Calculators and Guides
Specialist calculators are only useful when you understand the rules behind the numbers. These guides explain what each professional calculator does, which inputs matter, how to read the result and where the official rules come from, covering payroll and tax, immigration and visas, housing, business compliance, engineering and science. Every guide links to a free tool that runs in your browser and keeps your figures private.
318 guides
Pro Calculators and Guides
How to Sort Lines Alphabetically, by Length or by Number (and Remove Duplicates)
Paste a list and sort it A to Z, Z to A, by length or by number, trim spaces and remove duplicate lines in one step.
Pro Calculators and Guides
How to Split an Image Into a Grid for an Instagram Profile or Puzzle
Cut one picture into equal tiles such as 3 by 3 or 1 by 3, preview the lines and download all the pieces as a ZIP in order.
Pro Calculators and Guides
How to Straighten a Tilted Scan or Document Photo (Deskew)
Automatically detect the tilt of text lines in a scanned page or photo and rotate it straight, free and in your browser.
Pro Calculators and Guides
How to Test Left and Right Speakers or Headphones Online
Play a tone in the left, right or both channels and change frequency and wave shape to check your speakers or headphones.
Pro Calculators and Guides
How to Test Your Microphone Online Before a Call or Interview
Check that your microphone works, see the sound level and record five seconds to hear how you sound. Nothing is uploaded.
Pro Calculators and Guides
How to Translate Text to Morse Code and Back (With Sound)
Convert words to Morse code with dots and dashes, decode Morse to text, and play it as beeps. Includes the alphabet and timing rules.
Pro Calculators and Guides
How to Turn a PDF Into One Long Scrolling Image for Chat and Social Media
Combine all pages of a PDF into a single tall picture, choose width and gap, and share as JPG or PNG. Works for up to 60 pages.
Pro Calculators and Guides
How to Turn a Photo Into Pixel Art (Retro Game Style)
Pixelate a picture with larger blocks and fewer colours for a retro game look, and download it as a PNG with sharp edges.