How Many Days Can Your NVR Record? Storage, Resolution & Retention

Retention = disk ÷ bitrate ÷ channels ÷ hours. Use the free calculator to size an NVR or NAS before you buy, and learn the H.265 and motion tricks that double your days.

Published 2026-08-14

How Many Days Can Your NVR Record? Storage, Resolution & Retention

"How long will it record?" is the first question after "how many cameras". The answer is maths, not guesswork.

The retention formula

Storage used per day ≈ bitrate (Mbps) × 3600 × 24 × channels ÷ 8 ÷ 1024 GB. Divide your disk TB by that to get days. Resolution and codec drive the bitrate: 2MP H.264 ≈ 4 Mbps, 4MP ≈ 6, 8MP ≈ 12; H.265 roughly halves all three.

Two tricks that double your days

H.265 codec: about half the bitrate of H.264 for the same picture.
Motion recording: record continuously only at gates/entrances; motion-only elsewhere cuts average write by 60–70%.

Size before you buy

An 8-channel NVR with a single disk suits 7–14 days at 4MP; a 16-channel site or a 4-bay NAS reaches 30+ days. Run your numbers in the NVR storage calculator first — it does the maths for you.

Plan retention to policy

Pick the days you must keep (check local rules for shops/schools), then choose disk size to match. Our campus guide shows a motion-scheduled example.

Frequently asked

How much storage does a 4MP camera use per day?

Roughly 60–65 GB/day at 25fps H.264 continuous; about half that with H.265. Eight cameras therefore use ~0.5 TB/day on H.265 before motion scheduling.

How do I get more recording days without buying disks?

Switch to H.265 and use motion recording on low-traffic cameras. Both can roughly double retention from the same disk.

Are SurveilForge accessories compatible with Hikvision, Dahua and Axis cameras?

Yes — they follow open surveillance standards (IEEE 802.3af/at PoE, RJ45, BNC, DC 12V/24V) and work with any brand using those standards, including Hikvision, Dahua and Axis. SurveilForge is an independent brand, not affiliated with any camera OEM.