Free File Converters — The 10 Best Tools for Documents, Images, Audio and Units
Searching for a free file converter brings up ad-heavy sites and sponsored lists with out-of-date figures. We read the main comparison pages on the web — PC Tech Magazine, iTechGuides, PCsteps, MakeUseOf, How-To Geek, GIGAZINE, SmartUpWorld, schieb.de and Down Beach News — and in October 2026 checked every tool on its official site: licence, platforms, real free limits and where files go.
An engineer converts files every week: DOCX to PDF for a submission, hundreds of HEIC site photos to small JPGs for a report, TIFF scans to PDF, a meeting recording to MP3, and kilonewtons per square metre to pascals. Two questions matter more than formats: may you use the tool at work, and do your drawings get uploaded to someone else’s server? So for each tool we list advantages and disadvantages, and for online services, when your files are deleted.
Comparison table: the top 10
| Tool | Platforms | Licence in plain words | Best for |
|---|---|---|---|
| LibreOffice | Windows, macOS, Linux | Open source, free for any use | Office documents to PDF and back |
| Pandoc | Windows, macOS, Linux | Open source, free for any use | Markdown, Word and LaTeX between formats |
| File Converter | Windows | Open source, free for any use | Quick right-click conversion |
| XnConvert | Windows, macOS, Linux | Free for private and educational use only; paid for companies | Batch image processing with a GUI |
| ImageMagick | Windows, macOS, Linux | Free for any use, including commercial | Image conversion in scripts |
| IrfanView | Windows | Free for private, educational and charity use; paid in a business | Fast image viewing and conversion |
| calibre | Windows, macOS, Linux | Open source, free for any use | E-books and manuals |
| Qalculate! | Windows, macOS, Linux | Open source, free for any use | Calculations and conversions with units |
| fre:ac | Windows, macOS, Linux | Open source, free for any use | Batch audio conversion |
| VERT | Browser | Open source, free for any use | Converting in the browser without uploading |
The top 10
1. LibreOffice
A full office suite that opens and saves DOCX, XLSX and PPTX, exports to PDF and converts between Office formats and the open ODF formats. It can also run from the command line without a window and convert a whole folder of documents to PDF in one go.
Advantages: open source (MPL-2.0), free for any use including commercial, no registration. Runs on your computer and supports Hebrew.
Disadvantages: complex layouts (nested tables, text boxes, missing fonts) may shift. A heavy install for one conversion, and no DWG support.
2. Pandoc
A command-line tool that converts documents between dozens of formats: Markdown, Word and ODT, LaTeX, HTML, EPUB and PowerPoint. Engineers write reports in plain text and publish them as Word or PDF in the organisation’s template.
Advantages: open source (GPL-2.0), free for any use. Easy to script, with your own templates and filters.
Disadvantages: no graphical interface. PDF output needs an extra engine (LaTeX or an HTML engine), and complex DOCX layouts are not fully preserved.
3. File Converter
A small Windows tool that adds conversion and compression options to the right-click menu in File Explorer. Select one file or a hundred and get PNG, JPG, WebP or AVIF images, MP4, WebM or GIF video or MP3 audio without opening a program.
Advantages: open source (GPL-3.0), free for any use. Works offline, with your own presets.
Disadvantages: Windows only. Converting Office documents requires Microsoft Office to be installed, and there are few options for tuning codecs and quality.
4. XnConvert
A batch image converter: you build a chain of actions from more than 80 options — resize, crop, rotate, colour correction, text or watermark, metadata editing — and run it on a whole folder. It suits shrinking hundreds of site photos for a report or converting TIFF scans to JPG or PDF.
Advantages: reads more than 500 formats and writes about 70, presets and a watch folder, no adware or spyware, on Windows, macOS and Linux.
Disadvantages: free only for private or educational use, including non-profits; company use needs a paid licence, from 15 euros per licence. The interface is dense with options.
5. ImageMagick
A suite of command-line tools and programming libraries that converts between more than 200 image formats, resizes, crops, rotates, adds text. Useful in scripts that shrink hundreds of site photos.
Advantages: free for any use, including commercial use and inclusion in products.
Disadvantages: no convenient GUI, so you have to learn the commands, and a batch-script mistake can overwrite originals.
6. IrfanView
A tiny, very fast image viewer for Windows with batch convert, resize and rename, scanning and basic editing. Handy for sorting hundreds of site photos and converting the ones you need in a few clicks.
Advantages: small, fast and opens many formats, with plug-ins for more.
Disadvantages: Windows only, with a dated interface. Free only for private non-commercial, educational and charity use; business use needs a paid licence (US$18 or EUR 15 per user, perpetual).
7. calibre
An e-book library manager that converts between EPUB, MOBI, AZW3, DOCX, PDF and other formats, with a built-in reader and editor. Handy for manuals on an e-reader or tablet.
Advantages: open source (GPL-3.0), free for any use, on all three desktop systems. A built-in server lets you reach the library from a phone.
Disadvantages: a large program for one conversion, and PDF input is the weak spot: tables, equations and drawings rarely come out clean.
8. Qalculate!
A desktop calculator that understands units: type an expression such as force times lever arm with mixed units and get the result in the unit you choose. It includes thousands of units, physical constants, uncertainty and equation solving.
Advantages: open source (GPL-2.0), free for any use, with GTK and Qt interfaces and a command line.
Disadvantages: the number of options can overwhelm at first, and currency rates update only when you are online.
9. fre:ac
An open-source audio converter between MP3, M4A/AAC, FLAC, Opus, Ogg Vorbis, WMA, WAV and more. It converts whole libraries keeping folders and file names, and includes a CD ripper. Useful for converting meeting or measurement recordings to one compact format.
Advantages: free for any use including commercial, no registration and no advertising add-ons in the installer. Multi-core encoders and a portable USB edition.
Disadvantages: the last stable release (1.1.7) came out in March 2023, and since then only development builds have been published. The interface looks old.
10. VERT
A converter that opens in the browser but converts images, audio and documents on the computer itself (WebAssembly), so the files never leave the machine. It suits a quick HEIC or WebP to JPG conversion on a computer where you cannot install software.
Advantages: open source (AGPL-3.0), no registration, no ads and no count or file-size limit imposed by the service. Several files at once, downloaded as a ZIP; can be self-hosted.
Disadvantages: video is converted on the project’s server and deleted after download or after one hour. Fewer tuning options than desktop programs.
More free conversion tools worth knowing
Online conversion services: CloudConvert has the most advanced settings, cloud-drive links and an API. The free plan gives 10 credits a day, files up to 1 GB and up to 5 minutes of processing; Office to PDF costs 2 credits and PDF to Office costs 4, so in practice you get fewer than 10 conversions. Servers are in Germany; files are deleted at once with the delete button or automatically within 24 hours. FreeConvert works without an account: 20 conversion minutes a day, up to 5 minutes per file and files up to 1 GB, with ads; uploaded files are deleted automatically after 8 hours.
CloudConvert
Lunaweb GmbH
German online conversion service for 200+ formats, with 10 free credits a day and file deletion within 24 hours.
Get it from the vendor
FreeConvert
FreeConvert.com
Online conversion service for files up to 1 GB, with 20 free conversion minutes a day and automatic file deletion after 8 hours.
Get it from the vendorAn internal conversion server, and documents to text: ConvertX runs with Docker on an office server or NAS and works like a conversion website, but files stay on your network; it converts documents, images, media and even 3D models. Create the first account right after installing. Microsoft’s MarkItDown turns Office files and PDF into tidy Markdown — handy for pulling tables from a specification; no GUI, layout not kept.
ConvertX
C4illin (open-source project)
A file converter you host yourself with Docker, with a browser interface and support for over a thousand formats.
Get it from the vendor
MarkItDown
Microsoft
Python tool that turns Word, Excel, PowerPoint, PDF, HTML and EPUB into clean Markdown text with a single command.
Get it from the vendorUnit conversion: in ConvertAll you type any combination of units, such as litres per second, and it checks the dimensions and converts, with SI prefixes and engineering notation (no macOS version). GNU Units works on the command line, tracks units through a calculation and flags dimensional errors.
ConvertAll
Doug Bell
Flexible unit converter that lets you combine units freely, with SI prefixes, fractions and results in engineering notation.
Get it from the vendor
GNU Units
GNU Project (Adrian Mariano and contributors)
Command-line unit converter and calculator that tracks units through a calculation, with a database of thousands of units.
Get it from the vendorImages: Converseen is an open-source GUI on top of ImageMagick for batch conversion and resizing, including HEIC and turning a PDF into images. XnView MP and FastStone Image Viewer also batch-convert, but both are free for private and educational use only.
Converseen
Faster3ck
Convert and resize hundreds of images at once — prepare site photos and figures for reports, including PDF to images.
Get it from the vendor
XnView MP
XnSoft
A cross-platform image browser and batch converter supporting more than 500 formats, including RAW and HEIC.
Get it from the vendor
FastStone Image Viewer
FastStone Soft
An image browser and editor with side-by-side compare, batch convert and rename and annotation — free for personal and educational use.
Get it from the vendorAudio and video: FFmpeg for scripts; Shutter Encoder and HandBrake to convert and compress video with a GUI; Audacity to edit and convert recordings; VLC for a single file.
FFmpeg
FFmpeg project
A command-line engine for encoding, converting, cutting and compressing video and audio in almost any format, and the basis of most free video tools.
Get it from the vendor
Shutter Encoder
Paul Pacifico
An FFmpeg-based video, audio and image converter with a graphical interface, render queue, subtitles, lossless cutting and hardware acceleration.
Get it from the vendor
HandBrake
HandBrake team
Compress and convert large video files — screen recordings and site videos down to a shareable size.
Get it from the vendor
Audacity
Audacity Team
Audio recording and editing — narration for tutorials, plus a spectrogram for examining noise and vibration recordings.
Get it from the vendor
VLC media player
VideoLAN
An open-source media player that plays almost every video and audio format, with basic file conversion, no ads and no tracking.
Get it from the vendorPDF and CAD: PDF24 converts to and from Office, free for companies too. ODA File Converter converts DWG and DXF between versions, but non-members of the ODA may use it for non-commercial purposes only.
PDF24 Creator / PDF24 Tools
Geek Software GmbH
Free PDF toolbox: an offline Windows program plus a browser version — merge, split, compress, OCR, convert and a PDF printer.
Get it from the vendor
ODA File Converter
Open Design Alliance
Batch conversion of DWG and DXF files between versions, with audit and repair — free for non-commercial use only.
Get it from the vendorOutdated and misleading advice found on the web
- “CloudConvert: 25 conversions a day, deleted after an hour” — today 10 credits a day, files up to 1 GB, Office conversions use 2 to 4 credits, and automatic deletion is within 24 hours (or at once with the button).
- “FreeConvert has no limits” — there is a quota of 20 conversion minutes a day and 5 minutes per file. “Deleted after 24 hours” is also out of date: it is now 8 hours.
- “Convertio: up to 100 MB free” — the pricing page no longer publishes a clear free quota, so we left it out.
- “XnConvert is paid, from 15 euros” — that is only the company licence; private and educational use is free.
- Freemake, Zamzar, Format Factory, Switch and MediaHuman — capped file length, unpublished limits, installer add-ons or non-commercial use only. AhaConvert tops several lists, mostly in sponsored articles.
Which tool to choose for your need
Office documents to PDF: LibreOffice, including whole-folder conversion from the command line; PDF24 on Windows.
Plain-text reports: Pandoc; MarkItDown for the reverse direction.
Hundreds of site photos: at the office, ImageMagick or Converseen (free for companies too); for private use or study, XnConvert or IrfanView.
Quick conversions: File Converter on Windows; VERT on a computer where you cannot install anything.
Recordings and videos: fre:ac for batch audio, HandBrake or Shutter Encoder for video.
Units: Qalculate! for calculations, ConvertAll for quick conversions, GNU Units in scripts.
Confidential files — client drawings, contracts: only local tools, VERT (except video) or ConvertX on an internal server. CloudConvert and FreeConvert only for non-sensitive files.
Sources
- PC Tech Magazine — 10 Best Online File Converters in 2026: Free & Fast Picks
- iTechGuides — Best Image Converter Software in 2026: Researched & Ranked
- PCsteps — The Best File Converter for PDF, Media & More
- MakeUseOf — I finally found a way to convert files offline, and it’s surprisingly easy
- How-To Geek — This Self-Hosted File Converter Solved My WebP Woes
- GIGAZINE — VERT.sh: free, ad-free file converter that runs in your browser
- SmartUpWorld — 10 Best Free Audio Converter Software for Windows and Mac
- schieb.de — Audioformate konvertieren: Die besten Tools 2026
- Down Beach News — CloudConvert vs FreeConvert: Which One is Better
All the tools in one place: free productivity software.