We really appreciate all the feedback that we get through our contact form each day. A question that comes up quite often is “What is the maximum recording time of camera XY”, or, “How much recording time do I get with a 32GB card (16GB card, etc.)?”.
The answer to this question applies not only to dashboard cameras of course, but to any digital video camera. This article will show you how to calculate exactly how much video footage you are going to get with any given camera setup, and we will also give you a simple rule-of-thumb formula that allows you to all but calculate the recording time in your head.
NOTE: If you don’t care about the maths and just want a quick and dirty formula to calculate the recording time of any camera, just skip the next couple of paragraphs and continue reading at “Quick Formula”.
The reason why we do not usually state the recording capacity of the cameras is in the reviews is because it depends on several factors. One factor is of course the size of the memory card (SD card) used, and the other factor is the camera’s bit rate. When both of these are known, you can calculate the maximum recording capacity using a simple formula.
Bear in mind that you can reduce the bit rate by lowering video resolution. For example, if your camera’s maximum resolution is 1080p but you set it to 720p, obviously this will allow you to record more video footage than when you record in 1080p mode.
Calculating Recording Time
So based on the size of the memory card and the bit rate, how can we calculate the total recording time?
Let’s say you are using a DOD LS300W with a 32 GB SD card. You are running your device at a 1080p resolution for best video quality, resulting in a bit rate of approximately 15 Mbps. Mbps means “Megabit per second”, so each second of video consumes 15 million bits.
32 GB are 32 Gigabyte, or 32 billion bytes. 1 byte has 8 bits, so the capacity in bits is 32*8=256 Gbits. Divide this by 15 Mbits and the result is the number of seconds you can record.
32,000,000,000*8⁄15,000,000 = 32,000*8⁄15 = 256,000⁄15 = 17,066.67
17,066.67 seconds divided by 60 are 284.44 minutes, which equals 4.74 hours, or 4 hours and 44 minutes.
So with GB being the card size in GB, Mbps the bit rate in Mbps, and s the recording time in seconds, our formula is
GB*8*1000⁄Mbps = s
or to get the result in hours directly
GB*8*1000⁄Mbps*3600 = 2.222*GB⁄Mbps
If you just need a quick approximation of the total recording time in hours, of a dash cam or any other digital video camera, you can use this quick formula:
In other words, take the memory card capacity in GB, divide it by the bit rate, and multiply the result by 2.
The result will be about 10% less than the actual recording time.
So Which Dash Cams Have The Highest Recording Capacity?
Of the dash cams reviewed here, the one that will record longest at its maximum resolution is the Lukas LK-7900 ARA.
With a 256 GB memory card and a bit rate of approximately 11Mbps at 1080p, using our formula we get a total recording capacity of
2.222* 256GB⁄11Mbps = 51.712 hours
or in other words, a whopping 51 hours, 42 minutes and 43 seconds!
(Of course when you actually record, you may not get that full value because there will also be a small percentage of formatting data on the card.)