Video File Size Calculator

It converts your duration from minutes to seconds, multiplies that by the bitrate in megabits per second to get total megabits, then divides by 8 to convert megabits to megabytes. This is why resolution and frame rate don't directly appear in the file size formula itself — they only matter because they influence what bitrate you should choose.

Data per Frame divides your bitrate by frame rate, so the same per-second data budget gets split across more individual frames as frame rate rises. At 8 Mbps, 30fps gives each frame more data to work with than 60fps does, which is why doubling the frame rate without raising the bitrate tends to reduce per-frame quality.

It's a rough H.264 baseline table (5 Mbps at 720p up to 80 Mbps at 8K) scaled proportionally by your frame rate relative to 30fps — it's meant as a starting point for acceptable quality, not a hard target. Actual visually-lossless bitrates vary a lot by codec, since newer codecs like H.265 or AV1 can hit comparable quality at roughly half the bitrate this suggests.

This calculator assumes constant bitrate (CBR) encoding, where the file uses the exact same data rate throughout. Many cameras and encoders instead use variable bitrate (VBR), which allocates more data to complex scenes and less to static ones, so real-world file sizes for the same nominal bitrate setting can come in noticeably smaller or larger than this prediction.

It converts the card's capacity in gigabytes to megabits (capacity × 1024 × 8), divides by your bitrate to get total seconds of footage, then converts seconds to minutes. The same formula runs for 32GB, 64GB, 128GB, and 256GB cards to build the recording-time chart, so you can compare card sizes side by side at your chosen settings.