Security Camera Storage Calculator: Days of Recording, GB per Day and Drive Size
Estimate how many days of security camera footage your NVR or DVR drive holds, the GB per day, the drive size for 30 days (or any retention), and a bitrate estimate from resolution, frame rate and H.264/H.265 codec, with motion recording and RAID.
How it works
GB per camera per day = bitrate (Mbps) ÷ 8 × 3,600 ÷ 1,000 × hours recorded · GB per day = × cameras · Days = usable drive GB ÷ GB per day · Drive for N days = GB per day × N · Estimated bitrate = table kbps (H.264, 60 fps) ÷ frame-rate divisor × codec factor (H.265 0.5, H.265+ 0.35)
Recorded video size depends on the bitrate: the stream’s megabits per second. Divide by 8 to get megabytes, multiply by 3,600 seconds and the hours recorded each day, then by the number of cameras. The drive’s capacity divided by that daily figure is how many days the recorder keeps before it starts overwriting the oldest footage. Resolution, frame rate and codec matter only through the bitrate they produce. If you do not know the bitrate, choose Estimate it: the calculator uses a published surveillance table of typical H.264 bitrates at 60 fps, divides by a factor for lower frame rates (1.25 at 30 fps, 3 at 15 fps) and multiplies by 0.5 for H.265 or 0.35 for smart H.265+ codecs. Real bitrates swing with the scene, so treat it as a planning figure and read the actual bitrate from your NVR. Under More options, set the share of time with motion if you record on motion only, and add drives or a RAID layout: RAID 1 halves the space, RAID 5 gives up one drive and RAID 6 two. Drive sizes are decimal (1 TB = 1,000 GB); recorders often show binary TiB, about 9% lower, for the same space.
Worked example
Four cameras at 4 Mbps recording 24 hours a day: each uses 4 ÷ 8 × 3,600 ÷ 1,000 = 1.8 GB per hour, or 43.2 GB per day, so the four use 172.8 GB per day. A 4 TB (4,000 GB) drive holds 4,000 ÷ 172.8 = 23.1 days. Keeping 30 days needs 172.8 × 30 = 5,184 GB, or 5.18 TB, so buy a 6 TB drive.
Sources: CCTV Camera Pros: Video storage calculator for DVRs and NVRs (bitrate table, codec and motion factors) · Nelly’s Security: Security camera storage, bitrate and resolution guide · Wikipedia: Bit rate (size = bitrate × time ÷ 8)
Frequently asked questions
How much storage does a security camera use per day?
At 24-hour recording, every 1 Mbps of bitrate uses 10.8 GB per day. A 1080p camera at 2–4 Mbps uses about 22–43 GB per day, and a 4K camera at 8–16 Mbps about 86–173 GB per day. Motion-only recording cuts that in proportion to the time recorded.
How many days will a 1 TB or 2 TB drive record?
Divide the drive by your daily use. Four 1080p cameras at 2 Mbps recording continuously use 86.4 GB per day, so 1 TB lasts about 11.6 days and 2 TB about 23 days. At 4 Mbps those figures halve.
Does H.265 really halve the storage?
Roughly. H.265 (HEVC) needs about half the bitrate of H.264 for similar picture quality, and smart codecs such as H.265+ lower it further on static scenes by sending fewer full frames. The calculator uses 0.5 and 0.35 of the H.264 bitrate as typical factors.
Does motion detection save much space?
Often a lot. If a camera sees movement for about 6 hours a day, motion recording uses about a quarter of the space of 24/7 recording, so retention roughly quadruples. Busy streets, trees and false triggers reduce the saving.
Why does my NVR show less space than the drive label?
Drive makers count 1 TB as 1,000,000,000,000 bytes, while many recorders and computers show binary terabytes (TiB) of 1,099,511,627,776 bytes. A 4 TB drive therefore shows about 3.64 TiB. The footage capacity is the same; only the unit differs.
How long should I keep security footage?
Many homes and small businesses keep 30 days, enough to notice and review an incident. Some insurers, landlords or local rules ask for a set period, so check what applies to you.
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This calculator is for educational purposes. Double-check important results before acting on them.