Recording time calculator
How long a card actually records, worked out from capacity and bitrate. Capacity is the only card property that affects it — read and write speed decide whether the card keeps up, not how long it lasts.
A 512GB card holds about 2h 51m at 400 Mbps, or 5h 41m at 200 Mbps. Halve the bitrate and you double the time.
About 2 h 39 min after formatting, and less again if the codec runs variable bitrate or records audio alongside the video.
Recording time by capacity and bitrate
Hours and minutes at a constant bitrate, before the ~7% formatting overhead.
| Card | 100 Mbps | 200 Mbps | 400 Mbps | 800 Mbps | 1 Gbps | 2 Gbps | 4 Gbps |
|---|---|---|---|---|---|---|---|
| 128GB | 2h 51m | 1h 25m | 43m | 21m | 17m | 9m | 4m |
| 256GB | 5h 41m | 2h 51m | 1h 25m | 43m | 34m | 17m | 9m |
| 512GB | 11h 23m | 5h 41m | 2h 51m | 1h 25m | 1h 8m | 34m | 17m |
| 1TB | 22h 45m | 11h 23m | 5h 41m | 2h 51m | 2h 17m | 1h 8m | 34m |
| 2TB | 45h 31m | 22h 45m | 11h 23m | 5h 41m | 4h 33m | 2h 17m | 1h 8m |
| 4TB | 91h 1m | 45h 31m | 22h 45m | 11h 23m | 9h 6m | 4h 33m | 2h 17m |
How this is calculated
Bitrate is measured in megabits per second, while card capacity is sold in gigabytes. One gigabyte is 8,000 megabits (decimal, the way cards are marketed), so:
minutes = (capacity_GB × 8000) ÷ bitrate_Mbps ÷ 60
A 512GB card is 4,096,000 Mbit. At 400 Mbps that divides to 10,240 seconds — 2h 51m. The figures here assume constant bitrate and no overhead, which is why your camera will usually report slightly less.
Picking a card from this
Recording time tells you how much capacity you need. It says nothing about whether a card can sustain the write — a card can hold three hours of footage at a bitrate it cannot actually keep up with. Check the sustained write rating against your camera's bitrate, and leave headroom: sustained ratings are minimums, and heat or fragmentation can erode them.
Recording time questions
- How long can a 512GB card record?
- At 400 Mbps a 512GB card records about 2h 51m. Lower the bitrate and it lasts longer: about 5h 41m at 200 Mbps, or 1h 8m at 1 Gbps. The only inputs that matter are capacity and bitrate — not the card's brand or its peak read speed.
- How long can a 1TB card record in 4K?
- A 1TB card records roughly 5h 41m at 400 Mbps and 11h 23m at 200 Mbps. "4K" alone does not determine bitrate: an intra-frame codec at 4K can run several times the bitrate of a long-GOP one, so check the camera's actual recording bitrate rather than the resolution.
- How do you calculate recording time from bitrate?
- Bitrate is megabits per second, so convert the card to megabits (1 GB = 8,000 Mbit) and divide by the bitrate. A 512GB card is 4,096,000 Mbit; at 400 Mbps that is 10,240 seconds, or about 2 hours 51 minutes. Subtract roughly 7% for formatting and filesystem overhead.
- Why does my camera show less time than this?
- Three reasons: formatted capacity is about 7% smaller than the vendor figure, many codecs run variable bitrate and spike above nominal, and cameras reserve space for proxy files, thumbnails and clip metadata. Treat the estimate as a ceiling, not a promise.