How this calculator works
Each camera group starts from a typical H.264 bitrate for its resolution at 30 fps in a moderately busy scene. That figure is then scaled for codec, frame rate and scene activity:
Mbps per camera = base × codec factor × (fps ÷ 30)0.8 × scene factor
Bitrate does not drop in a straight line with frame rate, because each keyframe still costs the same, so the calculator uses a 0.8 exponent instead of a straight ratio. Storage per day is the bitrate multiplied by recorded seconds:
GB per day = Mbps × hours × 3600 × recording % ÷ 8 ÷ 1000
| Resolution | H.264 | H.265 | H.265 smart |
|---|---|---|---|
| 2MP | 4.0 | 2.2 | 1.4 |
| 4MP | 6.0 | 3.3 | 2.1 |
| 5MP | 7.5 | 4.1 | 2.6 |
| 8MP / 4K | 12.0 | 6.6 | 4.2 |
Base bitrates in Mbps at 30 fps, medium scene. Low-activity scenes use 0.6× and busy scenes 1.6×.
Drive counts allow about 7% for the gap between marketed TB and formatted capacity, keep the array below the maximum fill you set, and add parity drives for RAID 5 (one) and RAID 6 (two). RAID 1 and RAID 10 double the drive count.
Frequently asked questions
How much storage does a 4MP camera use per day?
Recording continuously in H.265 at 15 fps in a typical scene, a 4MP camera writes about 1.9 Mbps, which is roughly 20 GB per day or 600 GB over 30 days. Busy scenes, night-time noise and higher frame rates can double that.
Does H.265 really halve the storage?
For most scenes it saves 40–50% against H.264 at the same quality. Vendor smart codecs (variable keyframe intervals and region-based bitrate) can save more on static scenes, but savings shrink when the scene is busy.
Should I use motion recording to save space?
Event recording can cut storage by 60–80% on quiet sites. The trade-off is missing footage when motion detection misses an event, so many installers record continuously on entrances and use event recording elsewhere.
Why does the actual NVR fill faster than the estimate?
Night-time sensor noise, rain, trees moving and IR reflections all raise the bitrate. Check the real per-channel bitrate on the NVR a week after install and adjust retention or the bitrate cap.