Converting a file or a measurement is usually a means to an end: a form only accepts PDF, a recipe uses cups when your scale shows grams, or a video will not play on a relative's phone. Picking the right target format and the right tool saves you from blurry images, broken layouts, and privacy surprises. This guide covers the main types of conversion and what to watch for with each.
Lossless vs Lossy: The Key Idea
Every conversion is either lossless or lossy:
- Lossless conversions keep all the original information. Converting centimetres to inches, or a PNG to another lossless format, can be reversed exactly.
- Lossy conversions discard information to save space. Saving a photo as JPEG or a video as MP4 throws away detail you usually cannot see. Converting lossy files again and again compounds the loss, like photocopying a photocopy.
Rule of thumb: keep an original master copy, and convert from the master each time rather than from a previous conversion.
Document Conversions
PDF to Word
Useful when you need to edit a document you only have as a PDF. Text-based PDFs, the kind created by exporting from Word or Google Docs, convert well. Scanned PDFs are images of pages, so they need optical character recognition (OCR) to become editable text. Our PDF to Word guide covers this in detail. Note that the ToolGhost PDF to Word converter sends your file to a conversion service to produce the DOCX, so avoid using it for highly confidential documents.
PDF to Excel
Pulling tables out of PDFs saves retyping, but results depend on how the table was built. See the PDF to Excel guide for clean-up techniques. The PDF to Excel tool extracts text into rows in your browser, with one sheet per page.
PDF to images
Turning PDF pages into images is handy for slides, social posts, or previews. Choose PNG for pages with text and sharp lines, and JPEG for photographic pages where a smaller file matters more. Try PDF to Image.
Image Formats
| Format | Best for | Notes |
|---|---|---|
| JPEG | Photographs | Lossy, small files, no transparency |
| PNG | Screenshots, logos, text, transparency | Lossless, larger for photos |
| WebP | Websites | Supports both lossy and lossless plus transparency; smaller than JPEG and PNG at similar quality |
The Image Compressor can re-save images as JPEG, PNG, or WebP with a quality slider, entirely in your browser.
Video and Audio
MP4 with H.264 video is the safest choice for compatibility: it plays on virtually every phone, browser, and TV. WebM is efficient for websites. Extracting audio as MP3 is useful for podcasts or music practice. Video conversion is demanding, so the ToolGhost Video Converter uses a cloud conversion service: your video is uploaded, converted, and returned for download.
Units and Measurements
Unit conversion is lossless in principle, but mistakes are common because some units share names. A US gallon is 3.785 litres, while an imperial gallon is 4.546 litres. A US fluid ounce is 29.57 ml, but an imperial fluid ounce is 28.41 ml. The Unit Converter covers length, weight, temperature, area, volume, speed, time, and energy. Our unit conversion guide explains the exact definitions behind these units.
Cooking conversions
Converting cups to grams depends on the ingredient, because a cup is a volume and grams measure weight. One US cup of all-purpose flour weighs about 125 g, while a cup of granulated sugar is about 200 g. The Cooking Unit Converter uses ingredient-specific values rather than one generic figure.
Currency
Exchange rates change constantly, and the rate you get from a bank or card provider includes a margin over the mid-market rate. The Currency Converter uses mid-market rates for 160+ currencies, updated once a day, which is ideal for budgeting a trip or checking a price. For an actual payment, check the exact rate with your bank or payment provider.
Text Case
Changing text between UPPERCASE, lowercase, Title Case, and Sentence case is quick with the Text Case Converter. Title Case rules differ between style guides, so check whether short words such as "and" or "of" should be capitalised for your purpose.
Privacy: Does the Converter Upload Your File?
Online converters work in one of two ways:
- In your browser: The file is processed on your own device and never sent anywhere. At ToolGhost this applies to the image tools, merge, split, and compress PDF, PDF to Excel, and all calculators and unit converters.
- On a server: The file is uploaded, converted remotely, and sent back. This is needed for heavy tasks such as video conversion and high-fidelity PDF to Word, which ToolGhost handles through a conversion service.
For contracts, medical records, or anything confidential, prefer browser-based tools or desktop software you trust.
A Quick Conversion Checklist
- Confirm the format the recipient or website actually requires.
- Keep the original file.
- Choose lossless formats for anything you will edit again.
- Open and check the converted file before sending it.
- Consider privacy before uploading sensitive documents.
Frequently Asked Questions
Why does my converted Word document look different from the PDF?
PDFs record exact positions on a page, while Word flows text. Complex layouts with columns, text boxes, and tables often need manual tidying after conversion.
Does converting an image to PNG improve its quality?
No. Converting a JPEG to PNG keeps the existing quality but cannot restore detail that JPEG compression already removed.
Are unit conversions exact?
Many are exact by definition, such as 1 inch = 2.54 cm. Displayed results may be rounded, so keep extra decimal places for engineering or scientific work.