M4B to WMA Converter

Convert M4B to WMA: What This Tutorial Covers

This is a legacy-target conversion: you take a DRM-free .m4b audiobook and write it as .wma because a specific Windows Media-era player, in-car head unit, or library import expects that extension. The tutorial covers the two things that catch people out — the chapter list does not survive, and the "Variable Bitrate" control on this page is not really variable — plus how to pick a bitrate that keeps a twelve-hour book to a sensible size. If nothing on your side actually demands .wma, M4B to MP3 is the more portable target.

How to Convert M4B to WMA

1. Upload Your M4B File: Drag and drop the .m4b onto the page or click "Add Files". Audiobooks that ship as several part files can be queued together and run with the same settings.
2. Confirm the Audio Codec: Open Advanced Options; the Audio Codec dropdown offers WMA v2 (the standard Windows Media Audio encoder, and the setting this page starts on) and WMA v1. Leave it on WMA v2 unless you are feeding hardware that predates it.
3. Set the Bitrate under File Compression: The page opens on Quality Preset, but for spoken word you want a number. Switch to Constant Bitrate and choose from the list (8 kbps up to 384 kbps), or use Custom Bitrate to type an exact value. Specific file size works backwards from a target size instead.
4. Convert and Download: Click Convert and save the .wma. No sign-up, no watermark.

Walk-through: Choosing a Bitrate for a Long Audiobook

Bitrate is the only lever that meaningfully changes the output size, and audiobooks are long enough that the difference is measured in hundreds of megabytes rather than a few. The size is pure arithmetic — bitrate × duration ÷ 8 — so you can pick the row you want before you convert:

Microsoft's own documentation for the standard Windows Media Audio codec describes it as sampling "at 44.1 or 48 kilohertz (kHz) using 16 bits… offering CD quality at data rates from 64 to 192 kilobits per second" (About the Windows Media Codecs). Above 192 kbps you are past what Microsoft claims the codec needs; the dropdown goes to 384 kbps, but for narration decoded from a 64 kbps AAC source that is spent bytes.

Two more rules worth following. First, do not encode above the source: the M4B's AAC track already discarded detail, and a bigger WMA cannot bring it back. Second, set Audio Channel to Mono for single-narrator books — it roughly halves the data you need for the same perceived quality. Treat the bitrate you choose as a target rather than a guarantee; the finished file usually lands a little above the nominal rate.

What Each File Compression Mode Actually Does

The Variable Bitrate row is the one people get wrong. Standard Windows Media Audio has no true quality-targeted VBR mode in the encoder we run, so our pipeline resolves the range you pick to its average and encodes constant-bitrate at that figure. It is honest to say the control exists and misleading to say it varies.

Common Errors and How to Fix Them

• "My chapters are gone and it plays as one long file" — Expected. WMA's ASF container has no audiobook chapter table, so chapter markers and the resume position do not survive. To get navigable parts back, run Audio Cutter on the finished .wma at the timestamps you want.
• "The converter rejects my file" — Almost always DRM. Audible titles use AAX/AAXC protection and Apple purchases used FairPlay; encrypted audiobooks cannot be decoded by any online converter.
• "The cover image is missing" — Artwork travels inside an M4B as a still image track, and this conversion writes an audio-only file, so the picture is discarded.
• "The .wma won't play on my phone" — WMA is a Windows format. Android, iOS, and most browsers do not decode it. Reserve .wma for the device that demands it and use M4B to MP3 for everything else.
• "The audio sounds thinner than the original" — You went through a lossy-to-lossy re-encode: AAC is decoded to PCM, then WMA re-compresses it. Keeping the WMA bitrate at or slightly above the M4B's rate keeps that second pass inaudible for speech.
• "A 20-hour book is slow" — Upload time and encoding time both scale with duration. A twenty-hour title genuinely takes several times longer than a two-hour one; it is not stalled.

When This Doesn't Work

Two situations have no fix on this page. DRM-protected purchases stay protected — xconvert never strips encryption, so an Audible or Apple Books file has to be format-shifted through the vendor's own authorised route first, where your jurisdiction allows it. And if what you actually want is efficient speech compression rather than the .wma extension, note that Microsoft's answer for e-books, podcasts and voiceovers below 20 kbps was a separate codec — Windows Media Audio 9 Voice — which is not what this page produces. This page outputs standard Windows Media Audio, so for very low bitrates a modern speech-capable codec via the M4B converter hub will sound better at the same size.

Frequently Asked Questions

Will my audiobook keep its chapters after converting to WMA?

No. M4B stores chapters and the resume position in a dedicated track inside its MPEG-4 container, and the ASF container behind .wma has no equivalent structure that players read. The book becomes one continuous file with no chapter skip and no auto-resume. If chapter navigation is the point, keep the M4B, or convert to MP3 — MP3 can carry ID3 chapter frames — and split the file with Audio Cutter if your player still won't navigate it.

Can I convert a DRM-protected M4B from Audible or Apple Books?

No. Audible ships AAX/AAXC files with its own protection and Apple purchases historically carried FairPlay; both encrypt the audio so that only the vendor's app can decode it. Online converters cannot open them, and xconvert does not remove DRM. Only DRM-free .m4b files convert — books you encoded yourself, DRM-free purchases, and podcast or library downloads that were never protected.

Should I pick WMA v1 or WMA v2?

WMA v2 — the standard Windows Media Audio encoder, and what this page is set to. It is the more efficient of the two and is what any Windows Media stack from the past two decades expects. WMA v1 is the original release of the codec and only makes sense if you are feeding a device old enough to predate v2 support, which in practice means very early portable players.

Why does the Variable Bitrate option not produce a variable bitrate?

Because the encoder behind this page has no true quality-targeted VBR mode for Windows Media Audio. When you pick a range such as 96k-128k, our pipeline takes the midpoint — 112 kbps — and encodes at that constant rate. The result is a valid WMA, just not a variable-bitrate one, so there is no reason to prefer it over the Constant Bitrate list where you can see the exact number you are choosing.

What bitrate should I use for a spoken-word audiobook?

64 kbps mono is the sensible default: it is comfortable for narration and keeps a twelve-hour book around 346 MB. Drop to 32 kbps mono only when storage is the binding constraint and you can live with audible artefacts on "s" and "sh" sounds. Step up to 96-128 kbps stereo when the book has music beds or full-cast production. Encoding above the M4B's own bitrate just grows the file.

What sample rate should I choose?

Leave Audio Sample Rate on Original in almost every case — the source rate is what the narration was mastered at, and resampling adds nothing. Microsoft documents the standard Windows Media Audio codec at 44.1 or 48 kHz, so if a player is fussy those are the two explicit values worth trying. Lower entries in the dropdown (8000 to 24000 HZ) are for constrained telephony-style use and will audibly dull speech.

Does the cover art or the title and author survive?

The cover art does not — it rides in the M4B as an image track and this conversion writes audio only. Tag survival is not something to rely on either: plan to set title, author, and album in whatever library or player you load the .wma into, rather than expecting the audiobook's metadata to arrive intact.

How large will a 20-hour book be, and how are my files handled?

At 64 kbps a 20-hour book is about 576 MB; at 32 kbps roughly 288 MB. Files are uploaded over an encrypted connection, converted on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared or made public. The practical constraint on a long audiobook is upload and encode time, both of which scale with the length of the recording.