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Recording Time Calculator

Estimate how long available storage will last.

Advanced
%

Capacity you do not want to fill: formatting overhead, a safety margin, or an existing partial fill.

%

Overhead depends on your container and muxer. Leave this at 0 for the raw payload size, or enter a value you have measured.

Recording time

1:25:13
85.2242 min · 1 h 25 min 13 s
Total usable capacity
64.00 GB
Total bitrate used
100.128 Mbps
Capacity used per minute
750.96 MB

How this is calculated

The capacity is multiplied by the number of cards and reduced by the reserve to give the usable space. Removing the container overhead leaves the payload, which is turned into bits and divided by the total bitrate of the video and audio streams.

usableBytes     = capacityBytes × cardCount × (1 − reserveFraction)
payloadBytes    = usableBytes / (1 + overheadFraction)
payloadBits     = payloadBytes × 8
totalBitrateBps = videoBitrateBps + (includeAudio ? audioBitrateBps : 0)
durationSeconds = payloadBits / totalBitrateBps

Units

Bitrate is held in bits per second, capacity in bytes and duration in seconds. One byte is eight bits everywhere. Card capacities are decimal by default, matching how they are sold: 1 GB is 1,000,000,000 bytes. Switch Unit system to Binary to work in the GiB a camera or operating system usually reports.

Assumptions

  • The bitrate you enter is the average the camera actually writes.
  • Reserve and container overhead are 0% unless you set them.
  • Recording is continuous. Clip-splitting, file-system limits and card wear are not modelled.

Read how every number on this site is derived.

Worked example

A 64 GB card at 100 Mbps video with a 128 Kbps audio track, no reserve and no overhead:

usableBytes     = 64,000,000,000 × 1 × (1 − 0)  = 64,000,000,000 bytes
payloadBytes    = 64,000,000,000 ÷ (1 + 0)      = 64,000,000,000 bytes
payloadBits     = 64,000,000,000 × 8            = 512,000,000,000 bits
totalBitrateBps = 100,000,000 + 128,000         = 100,128,000 bps
durationSeconds = 512,000,000,000 ÷ 100,128,000 = 5,113.4547… s
minutes                                         = 85.2242 min
clock                                           = 1:25:13

This is test vector V3 in the calculator requirements. Minutes are shown to four decimal places so that a value like this one can be checked against the derivation.

Frequently asked questions

Why does my 64 GB card hold less than the calculator says?

Two reasons, and the calculator can model both. A card sold as 64 GB holds 64,000,000,000 bytes, which a camera or operating system reports as about 59.6 GiB. Formatting structures and any existing footage take more. Set Reserve under Advanced to the share of the card you do not intend to fill.

What does Reserve actually do?

It removes a percentage of the capacity before the calculation, so a 10% reserve on a 64 GB card leaves 57.6 GB of usable space. Use it for a safety margin, for formatting overhead, or when the card already holds material you are keeping.

Can I plan across several cards?

Yes. Number of cards under Advanced multiplies the capacity by a whole number between 1 and 1,000, so four 64 GB cards are treated as 256 GB of usable space. The result is the total recording time across all of them at the stated bitrate.

Does the camera record at exactly the bitrate I entered?

Rarely. Most cameras label a mode with a nominal bitrate and vary the real rate with scene complexity, and some hold a constant rate only in specific codecs. Treat the answer as a plan, not a guarantee, and keep a margin for the last clip.

Why is the time shown twice?

The clock reading is what you act on when planning a shoot, and the decimal minutes are what you check the arithmetic with. Both come from the same unrounded number of seconds, so they never disagree.