CCTV Storage Calculator

How CCTV storage actually works

A security camera records a constant stream of video, and every second of that stream takes up space. The bitrate — measured in megabits per second — decides how much. A 1080p camera typically records at around 1.2 Mbps, which means it writes roughly 12.7 GB to disk for every 24 hours of footage. Multiply that by the number of cameras and the number of days you want to keep, and you get the total storage your system needs. Most recorders (DVRs and NVRs) come with a hard drive already installed, but the default size is rarely enough for multi-camera setups. Knowing your real storage requirement before you buy saves you from the classic mistake: discovering after two weeks that your footage is being overwritten and the clip you needed is gone.

What affects recording size

Three things matter most. First, resolution: a 4K camera can use four times the storage of a 1080p one at the same frame rate. Second, recording hours: a shop that records only during opening hours needs half the space of a home recording around the clock. Third, compression: modern H.265 encoding roughly halves file sizes compared to the older H.264, so two identical cameras can have very different storage footprints depending on the codec. Frame rate and motion also play a role. A camera set to 15 frames per second instead of 30 uses noticeably less space, and motion-triggered recording only writes when something moves — perfect for quiet hallways and empty parking lots at night.

Worked example

Take a small office with 4 cameras, all recording 1080p Full HD at 1.2 Mbps, 24 hours a day, with 30 days of footage kept. Each camera uses 1.2 × 3,600 × 24 ÷ 8 ÷ 1,024 ≈ 12.7 GB per day. For 4 cameras that is about 50.6 GB per day, and over 30 days it reaches roughly 1,519 GB — about 1.48 TB. So a single 2 TB drive covers this setup with room to spare, while a 1 TB drive would start overwriting footage after about 20 days.

Practical tips to save storage

Start by matching resolution to the job: entry points deserve 1080p or higher, but a storage room camera can stay at 720p. Switch your recorder to H.265 if your cameras support it — the quality looks the same while storage drops by up to half. Use motion detection or scheduled recording for low-traffic areas instead of recording empty rooms around the clock. Finally, add a 15–20% buffer on top of your calculated total so you never lose footage to a surprise overwrite.