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Recording Time Calculator

Enter card capacity and bitrate to estimate record time.

Result

171 min
2.84 hr
45.00 GB/hr

How it is calculated

This works from the card's capacity to the time it lasts. First the bitrate in megabits per second is turned into data per minute: MB per minute = Mbps × 60 ÷ 8. Then minutes = card GB × 1000 ÷ MB per minute, hours = minutes ÷ 60, and the third result is the fill rate GB per hour = card GB ÷ hours. Units are decimal, so 1 GB = 1,000 MB, the way card makers state capacity. Minutes are rounded to whole numbers, hours and GB/hr to two decimals. Both inputs must be above zero. Enter the total bitrate of video plus audio, and note the usable space on a real card is smaller than the printed size.

Worked example

A 128 GB card recording at 100 Mbps. Data per minute: 100 × 60 ÷ 8 = 750 MB. Minutes: 128 × 1000 ÷ 750 = 170.67, shown as 171 min. In hours: 170.67 ÷ 60 = 2.84 hr. The fill rate is 128 ÷ 2.84, which is 45.00 GB/hr, meaning every hour of this footage takes up 45 GB. So the card holds about 2 hours 50 minutes before it is full, which is the planning figure for how many cards to carry.

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Common mistakes

  • Entering the bitrate in megabytes per second. The field is megabits (Mbps); a camera listing 100 MB/s would be 800 Mbps, so the result would be eight times too long.
  • Entering the bitrate in kbps. Convert first: 50,000 kbps is 50 Mbps.
  • Relying on the printed card size as fully usable. Formatting and file-system overhead leave a bit less, and cameras often stop slightly before the card is truly full, so plan for less than the displayed time.
  • Using the highest advertised bitrate for variable-bitrate recording. If the camera lowers the rate for simple scenes, the real recording time is usually longer than an estimate based on the maximum, so treat the result as a minimum.
  • Forgetting audio and other tracks. Add the audio bitrate to the video bitrate, or the card will fill a little sooner than computed.

About this calculator

Video files consume storage at a steady rate set by the bitrate — the number of megabits recorded per second of footage. Dividing a memory card’s total capacity by that bitrate (after converting both to matching units, typically megabits) gives the total recording time the card can hold before it fills up.

Higher-resolution and higher-frame-rate footage uses a higher bitrate and so eats through card capacity faster — 4K video at a high bitrate can fill a card many times quicker than 1080p — which is why videographers and photographers check this math before a shoot to make sure they’re carrying enough cards, or to pick the right card size for a job. Match your memory card's capacity against the camera's recording bitrate to estimate how many minutes of footage fit before the card is full.

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Comments (1)

  • Editorial team

    The time shown is how long the whole card lasts, not how long one clip can run. Many cameras split recording into files at 4 GB on FAT32 cards, and some stop at a fixed clip length, so a long event may arrive as several clips. The GB per hour line is handy for comparing bitrate settings. Which camera and bitrate do you shoot with?

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