OBS Replay Buffer Storage Calculator

What the Replay Buffer does

The OBS Replay Buffer keeps the last few seconds or minutes of your program in memory so you can press a hotkey and save what just happened. Unlike regular recording, it only writes to disk when you ask it to, which keeps disks quieter and avoids filling storage with uneventful footage. The OBS Replay Buffer Storage Calculator estimates the memory footprint of that rolling buffer, the file size when you save a clip, and how much headroom you should plan for.

How memory usage is calculated

Size is driven by the encoded data rate. Video bitrate in megabits per second converts to megabytes per second by dividing by eight. Add audio bitrate in kilobits per second (divide by 8000 to get MB/s), then multiply by your target buffer length in seconds. Finally, add headroom to cover normal variation from scene complexity, VBV behavior, container overhead, and metadata. The calculator defaults to 15% headroom, which is a practical starting point for CBR/VBR encoders used in OBS.

Choosing bitrates for common resolutions

For 1080p60 streaming, many creators target 6–10 Mbps for H.264 and can go lower with efficient HEVC if the platform supports it. For 1440p60, 10–14 Mbps is typical, and 4K60 often needs 14–25 Mbps for clean motion depending on content. If your scenes include fast camera pans, foliage, water, or noisy high-ISO sources, expect higher momentary data rates and plan more headroom. Remember to include audio: 160–192 kbps stereo AAC is common and small relative to video, but it still counts.

How disk size is estimated

When you save a replay, OBS writes the current buffer to a file in your chosen container (MKV is popular for crash safety). The file size is simply your total data rate multiplied by the clip length, plus a little container overhead. The calculator shows size for the current buffer and handy quick picks (10, 30, 60, 120 seconds) so you can judge download/upload impact or decide on disk allocation for highlight capture sessions.

Picking a smart memory limit

Replay Buffer memory doesn’t need to equal your system RAM, but you should leave plenty for the game, browser, plugins, and the OS. If you reserve 2048 MB for the buffer at 10 Mbps video and 160 kbps audio, you can keep roughly 25 minutes in memory with the default headroom. If the calculator’s “Max buffer with RAM” tile shows less time than you want, either increase installed memory, lower bitrate, or set a shorter buffer and save more frequently.

Workflow suggestions

• Use MKV or FLV while capturing, then remux to MP4/MOV in OBS after the session for easier editing.
• Bind a clear, unique hotkey for saving replays and test it before going live.
• Store replays on a fast SSD or NVMe; mechanical disks can stutter under heavy game loads.
• If bandwidth is your constraint, match your stream bitrate to platform guidelines and keep a separate, higher-quality local recording if needed.
• Monitor dropped frames, encoder queue, and VRAM usage; if they spike, reduce bitrate or resolution and recheck memory sizing.

Limits of this calculator

The tool assumes decimal units (1 MB = 1,000,000 bytes) and a single video track plus one audio track. It doesn’t model multi-track audio, HDR overhead, key-int. spikes, or exotic containers. Real-world file sizes vary slightly with content complexity and encoder settings; that’s why we surface headroom and encourage a quick test capture before going live.

Does the Replay Buffer hurt performance?

It stores compressed data in memory. At the same bitrate, memory use is similar to regular recording, but disk writes happen only when you save—often easier on storage.

Is MKV better than MP4 for replays?

MKV is resilient if the app or PC crashes mid-write. You can remux to MP4/MOV in OBS after the session.

What headroom should I use?

Start with 10–20%. If your content has heavy motion or you use VBR with a high max, push it higher.

Do I need FPS for sizing?

No—the encoded bitrate already includes motion. FPS is optional and shown only for context.