Audio storage calculator.
How much space do voice recordings actually take? Dial in your hours, quality and retention to see daily and monthly storage — and get a cleanup schedule that keeps your phone from filling up.
Your library tops out at 3.46 GB (3.9% of usable space). Set auto-cleanup to 30 days and forget about it; glance at storage once a month.
Storage is only half the question. Check whether your phone can record reliably for interruption risks and the setup steps your device needs.
Voice recording size per hour, day and month
Quick reference for common recorder qualities. “All day” assumes 8 hours of recording; “24/7” is continuous recording.
| Quality | Format | Per hour | All day (8 h) | 24/7 day | 24/7 month |
|---|---|---|---|---|---|
| BlackBox (default) | AAC 32 kbps mono, 16 kHz | 14.4 MB | 115 MB | 346 MB | 10.4 GB |
| Standard voice memo | AAC 64 kbps | 28.8 MB | 230 MB | 691 MB | 20.7 GB |
| High | AAC 128 kbps | 57.6 MB | 461 MB | 1.38 GB | 41.5 GB |
| Lossless | WAV 16-bit mono | 318 MB | 2.54 GB | 7.6 GB | 229 GB |
Formula: bitrate (kbps) × 0.45 = MB per hour. 64 kbps × 0.45 = 28.8 MB/h.
How the math works
Audio file size is bitrate × duration. A bitrate of 64 kbps means 64 kilobits — 8 kilobytes — every second. Multiply by 3,600 seconds and you get 28.8 MB per hour. Sample rate and channel count are already baked into the bitrate, so for compressed formats like AAC and MP3, bitrate is the only number that matters for size.
Why retention beats deleting by hand
If you record daily, your library grows forever — unless old audio expires automatically. With a retention window (say, 30 days), storage reaches a fixed ceiling and stays there: new recordings replace expired ones. That’s how 24/7 recording stays practical even on a 64 GB phone. If recordings are stopping rather than piling up, try the background recording troubleshooter.
Audio storage questions, answered
How much storage does one hour of audio recording use?+
At 64 kbps AAC — the sweet spot for voice — one hour is about 28.8 MB. Low quality (32 kbps) is ~14.4 MB/hour, high quality (128 kbps) is ~57.6 MB/hour, and uncompressed WAV (16-bit mono) is ~318 MB/hour. The formula: kbps × 0.45 = MB per hour.
How much space does 24/7 voice recording take per month?+
Recording around the clock at 64 kbps AAC uses about 691 MB per day, or roughly 20.7 GB per month. At 32 kbps that halves to ~10.4 GB per month — easily manageable on a 128 GB phone with a 30-day auto-cleanup rule.
What audio quality should I use for voice recording?+
64 kbps AAC mono is the sweet spot for speech: voices stay clear and transcription-ready while files stay small. Use 128 kbps if you also want room ambience or music, and 32 kbps only when storage is very tight.
What quality does BlackBox record at, and how much storage does it use?+
BlackBox records at 32 kbps AAC, mono, 16 kHz on both iPhone and Android — a speech-optimized setting that uses about 14.4 MB per hour. Recording 8 hours a day is roughly 115 MB daily, and even 24/7 recording is only ~10.4 GB per month before cleanup.
Will a 24/7 recorder app fill up my phone storage?+
Not if it manages retention. BlackBox records in the background and automatically deletes recordings older than your chosen retention window, so your library reaches a fixed size and stops growing — for example, 30 days of 8 h/day at BlackBox's 32 kbps settles at about 3.5 GB.
Which takes more space — MP3, AAC or WAV?+
At the same bitrate, MP3 and AAC files are the same size, but AAC sounds better at low bitrates, which is why modern recorder apps use it. WAV is uncompressed and roughly 10–20× larger — overkill for voice recording on a phone.
Never think about storage again. Get BlackBox.
BlackBox records your day in the background and cleans up after itself with automatic retention — private, on-device, free on iPhone and Android.