Estimate storage for action camera footage.
Action cameras record at fixed bitrates per mode, so storage is a straight function of time and mode: 4K60 at 100 Mbps is about 0.73 GB a minute, meaning a 128 GB card holds roughly two and a half hours. Working in minutes per card rather than gigabytes is the practical form, because on a shoot the question is always how long you can keep rolling.
Data rate by mode
GB per minute = bitrate Mbps x 60 / (8 x 1024), with 45 Mbps at 1080p60 rising to 120 Mbps at 5.3K60
Card capacity in time
Minutes per card = card capacity x 0.95 / GB per minute
Yes. High-bitrate modes require a sustained write speed, so a V30 or better rating is necessary; a slow card causes dropped frames or refuses the mode entirely.
Not exactly, because the encoder does not simply double bitrate — but it rises substantially. Compare the actual bitrate for each mode rather than assuming it scales with frame rate.