Tool · ReplayR

Storage Capacity & Buffer Time Calculator

How long a rolling buffer can run, and how many saved clips fit on your device — calculated from your resolution and free storage in seconds.

Enter your recording resolution and how much free storage your device has. The calculator shows how many hours of buffering your RAM can sustain, the file size per saved clip, and the total number of clips that fit on disk at your chosen clip length.

Want auto buffer management on your phone?

ReplayR handles storage automatically — rolling buffer in RAM, clips only on Save.

Get on Google Play

Calculate your buffer & storage

Recording resolution

Frame rate

Free storage on device (GB)

Rolling buffer length (seconds)

Saved clip length (seconds)

Manage buffer storage automatically — on your phone, offline

ReplayR keeps the buffer in RAM, writes to disk only on Save, and lets you swipe to keep or toss at session end — no storage waste, no cloud.

Get it on Google Play

How rolling buffer storage works

The buffer lives in RAM, not on disk

A rolling buffer records continuously to device RAM (working memory), not to internal storage. The camera writes new frames in a circular fashion — when the buffer is full, the oldest frames are overwritten. This means a 90-second buffer at 1080p/30fps uses roughly 90–120 MB of RAM, and that amount never grows no matter how long you run the session.

Saved clips are the only disk impact

When you tap Save, the current buffer window is written from RAM to internal storage as an MP4 file. That's the only moment storage is consumed. A 90-second clip at 1080p/30fps typically produces a 100–135 MB file. Five clips per session = roughly 500–700 MB per session, regardless of how many hours of sport you recorded around those clips.

Resolution has a compounding effect

Resolution affects both the RAM footprint and the size of every saved clip. Moving from 1080p to 4K roughly quadruples the bitrate (and thus the file size for any given duration). For coaching sessions where you're reviewing technique rather than archiving broadcast-quality footage, 1080p at 30fps gives excellent clarity at manageable file sizes — a 30-second clip is around 30–60 MB.

Frame rate doubles the data at any resolution

Shooting at 60fps doubles the number of frames captured compared to 30fps, which roughly doubles the bitrate and file size. The benefit is smoother slow-motion playback: a 60fps clip slowed to 0.25× plays back at 15fps (still smooth), whereas a 30fps clip at 0.25× drops to 7.5fps (jerky). For biomechanics analysis — golf swings, tennis strokes, gymnastic landings — 60fps is worth the storage cost.

Reference: typical Android camera bitrates

Resolution	FPS	Typical bitrate	MB per minute	30s clip size
480p	30	2 Mbps	15 MB	7.5 MB
720p	30	5 Mbps	37.5 MB	18.75 MB
1080p	30	8–12 Mbps	60–90 MB	30–45 MB
1080p	60	16–20 Mbps	120–150 MB	60–75 MB
1440p	30	17–25 Mbps	127–187 MB	64–94 MB
4K	30	40–60 Mbps	300–450 MB	150–225 MB
8K	30	80–160 Mbps	600–1,200 MB	300–600 MB

Bitrates vary by device, codec (H.264 vs H.265/HEVC), and scene complexity. H.265 typically halves the file size at equivalent quality. Values above are H.264 estimates for planning purposes.

How to use this calculator

Step 1 — Pick resolution

Choose the resolution you plan to record at. 1080p/30fps is the default — it covers the sweet spot for sports coaching analysis with manageable file sizes.

Step 2 — Enter free storage

Go to Settings → Storage on your Android phone and note how much free space you have. Enter that number in gigabytes. The calculator determines the total number of saved clips that can fit.

Step 3 — Set clip length

The clip length is how long each saved clip will be (defaults to 30 seconds). If you're saving full buffer windows of 90 seconds, enter 90. This affects both file size per clip and total clips storable.

Step 4 — Read results & plan

The results show buffer RAM usage, file size per clip, and how many clips fit. For automated buffer and storage management on your phone, ReplayR handles this natively — including offline use with no cloud uploads.

Storage planning scenarios

Tennis or padel session (1 hour)

At 1080p/30fps, saving 10 key rally clips of 30 seconds each uses roughly 300–450 MB. A phone with 5 GB free can hold 55–100+ such clips — equivalent to 20+ full tennis sessions before cleanup is needed.

Gymnastics coaching (2 hours)

Gymnastics coaches typically save 20–40 clips per session covering vault, beam, and floor skills. At 1080p/30fps with 30-second clips, a 2-hour session saves 600 MB–1.8 GB. Plan for 3–5 GB of free space per training block.

Martial arts (rolling / sparring)

BJJ rounds are 5–6 minutes — the 12-minute Pro buffer covers an entire rolling session. Saving three full rounds at 4K/30fps produces approximately 2.7–4.5 GB. Keep 15–20 GB free for multi-session storage before archiving.

Youth soccer (practice drills)

Coaches saving 15 drill clips of 45 seconds each at 1080p/30fps use approximately 1–1.5 GB per practice. A 32 GB device with 20 GB free can hold roughly 13–20 full practice sessions between purges.

Slow-motion analysis (60fps)

Shooting at 60fps for slow-motion playback doubles file sizes. A 15-second clip at 1080p/60fps is roughly 30–45 MB vs 15–22 MB at 30fps. Budget double the storage, but you gain the ability to slow clips to 0.25× smoothly.

Long-term archiving

If you keep every saved clip, storage fills over weeks. ReplayR's bin feature gives a 24-hour window to restore tossed clips (Pro). For permanent archives, use the Android share sheet to transfer to a NAS, external drive, or cloud service after each session.

FAQ

How much storage does a rolling video buffer actually use?

A rolling buffer uses only RAM — not disk storage. At 1080p/30fps with H.264 encoding (~8 Mbps), a 90-second buffer uses roughly 90 MB of RAM. That memory is recycled continuously; disk is only consumed when you tap Save.

What resolution should I use to maximise buffer length?

Lower resolutions extend buffer duration if RAM is limited, and dramatically reduce clip file sizes. For coaching analysis, 1080p is the practical sweet spot — good enough to see form details, small enough to save many clips. 4K is best reserved for high-precision biomechanical analysis where you need to zoom into specific body segments.

Where does ReplayR store saved clips?

Saved clips go to internal device storage (not a cloud service). The buffer runs entirely in RAM and is never written to disk unless you tap Save. This means a running buffer has zero impact on available storage — only explicitly saved clips do.

Is my data sent to a server when I use this calculator?

No. All calculations run entirely in your browser using JavaScript. No data is sent to any server. Your inputs are optionally saved in your browser's localStorage so the page remembers your settings on revisit.

How does bitrate affect clip file size?

File size (bytes) = bitrate (bits/second) × duration (seconds) ÷ 8. A 30-second clip at 8 Mbps = 30 MB. At 50 Mbps (4K), that same clip is 187 MB. H.265/HEVC produces similar quality at roughly half the bitrate of H.264 — but not all Android devices support HEVC recording.

Related tools & guides

Stop worrying about storage. Let ReplayR handle it.

ReplayR keeps the buffer in RAM, writes only what you keep, and lets you toss the rest at session end. Zero dead footage on disk.

Get it on Google Play Back to ReplayR