Estimate how much storage a recording system uses and how long its available space will last. Use the average bitrate for the chosen recording mode, not the advertised resolution alone. The answer is a planning estimate and becomes more useful when you replace assumed bitrates with observed ones.
The calculator uses camera count × average bitrate × recording time. At 4 cameras, 4 Mbps each and 24-hour recording, 2,000 GB holds about 11.6 days before reserve space. Explore buying guides.
The calculation
For decimal gigabytes, daily storage is camera count × average megabits per second × 10.8 × recording hours per day ÷ 24. Usable capacity is the entered capacity after the reserve percentage. Estimated retention in days is usable capacity divided by daily storage.
For example, four cameras averaging 4 Mbps each and recording 24 hours a day use about 172.8 GB per day. A 2,000 GB device with no reserve then holds about 11.57 days. Reserving 10% leaves 1,800 GB and reduces the estimate to about 10.42 days. These are arithmetic examples, not measurements of any named camera.
Choose inputs that match the recordings
Use the sum of the active streams when a system records front, rear and cabin video at different bitrates. You can model them as one combined stream or run separate calculations and add their daily usage. Audio, metadata, file overhead and recorder behavior may change the real result.
Recording hours means the actual time saved per day. For event recording, estimate the total retained clip duration rather than the number of hours the camera is powered on. Motion, image noise, compression settings and variable bitrate can make file sizes change. Compare a quiet day and a busy day before relying on one value.
Capacity and retention are different from endurance
A card’s size determines how much it can hold; its supported format, speed and recording endurance determine whether it is suitable for the camera. Check the exact device’s supported card list and capacity limit. Advertised decimal gigabytes can also differ from the units shown by a recorder.
After installation, record representative footage and inspect actual file growth and the oldest retrievable clip. Confirm how the system overwrites or protects files, and export something before you need it. Use the dash-cam card guide or camera memory-card guide for the buying checks that this estimate cannot establish.