How many days of footage will your system keep? The answer depends on four numbers: how many cameras you have, how much data each camera records per second, whether it records all the time or only on motion, and how big your drive is. You can estimate it with simple arithmetic. This guide gives you the formula, worked examples for 4, 8 and 16 cameras, advice on motion versus continuous recording, notes on RAID and drive types and common mistakes that leave owners with a week of footage when they expected a month.
The numbers below are estimates for planning. Real bitrates vary with camera settings, scene activity, lighting and compression. Ask your installer to confirm with the actual equipment.
1. The Short Version
| Item | Rule of thumb |
|---|---|
| Data per camera | Measured in megabits per second (Mbps). |
| Daily storage per Mbps | About 10.8 gigabytes per day for continuous recording. |
| Total storage | Cameras × bitrate × 10.8 GB × days. |
| Motion recording | Often cuts storage substantially, depending on activity. |
| Retention goal | 30 days is a common planning figure. |
| Always add margin | Plan for 15 to 25 percent extra. |
2. The Formula
One megabit per second recorded continuously for 24 hours equals about 10.8 gigabytes. So:
Storage in GB = number of cameras × bitrate in Mbps × 10.8 × days
Then convert to terabytes by dividing by 1,000. Add a margin for overhead and growth.
3. Typical Bitrates
Bitrates depend on resolution, frame rate, compression (such as H.264 or H.265) and scene complexity. As planning figures:
| Camera resolution | Typical bitrate range (H.265) | Typical bitrate range (H.264) |
|---|---|---|
| 2 MP (1080p) | 1 to 2 Mbps | 2 to 4 Mbps |
| 4 MP (2K) | 2 to 4 Mbps | 3 to 6 Mbps |
| 8 MP (4K) | 4 to 8 Mbps | 6 to 12 Mbps |
Busy scenes, night noise and high frame rates push bitrate up. Your installer can read the actual bitrate from the camera or recorder and use it for the calculation.
4. Worked Examples (Continuous Recording)
Four 4 MP cameras at 3 Mbps each, 30 days: 4 × 3 × 10.8 × 30 = 3,888 GB, about 3.9 TB. With 20 percent margin, plan on roughly 4.7 TB. A 6 TB drive would be comfortable.
Eight 4 MP cameras at 3 Mbps each, 30 days: 8 × 3 × 10.8 × 30 = 7,776 GB, about 7.8 TB. With margin, about 9.3 TB. A 10 TB drive fits tightly; 12 TB or two drives is safer.
Sixteen 4 MP cameras at 3 Mbps each, 30 days: 16 × 3 × 10.8 × 30 = 15,552 GB, about 15.6 TB. With margin, about 18.7 TB. Plan multiple drives or a RAID array.
Eight 8 MP cameras at 6 Mbps each, 30 days: 8 × 6 × 10.8 × 30 = 15,552 GB, about 15.6 TB. Doubling resolution roughly doubles storage.
5. Continuous vs. Motion Recording
Continuous recording captures everything. It is simple and avoids missed events but uses the most storage.
Motion recording records only when motion is detected. In a quiet area at night it can cut storage substantially, but busy areas such as streets and parking lots may trigger constantly. Poorly tuned motion settings can miss events.
Hybrid (pre-event buffering) records a few seconds before motion starts, so you see what led up to it.
Mixed schedules record continuously during business hours and by motion overnight, or the reverse.
If you plan on motion recording, ask for the estimated reduction based on your actual scene, not an optimistic number. Many owners use continuous recording for entrances and registers and motion for quiet areas.
6. Adjusting Settings to Stretch Storage
- Lower frame rate on cameras where fast action is unlikely.
- Use H.265 if the recorder and cameras support it.
- Use a substream for remote viewing so you don't stress the network.
- Set variable bitrate with a sensible cap.
- Reduce resolution on low-value cameras.
- Add storage instead of lowering quality at critical cameras.
Don't cut quality at entrances and registers just to save a few hundred dollars on drives.
7. Drive Types, RAID and Reliability
Surveillance-rated drives. Built for continuous writing. Regular desktop drives can fail faster.
RAID. Combines drives so one failure does not lose footage. Common levels include RAID 1 (mirroring) and RAID 5 or 6. RAID uses extra capacity for redundancy, so plan for usable capacity, not raw capacity.
Hot spares. A spare drive that takes over automatically.
Replacement schedule. Drives wear out. Many installers plan to check or replace them every few years. See our guide on maintenance.
Backup. RAID is not backup. For critical clips, save copies elsewhere.
Cloud backup. Optional for selected clips. See our guide on cloud vs. local storage.
8. How Many Days Do You Need?
Thirty days is a common planning figure for homes and many businesses. Consider longer periods (45 to 90 days) if you:
- Handle cash or have frequent disputes.
- Receive claims after long delays.
- Travel for long periods.
- Operate seasonally.
- Have regulatory or contractual requirements.
See our guide on how long to keep footage.
9. Expansion Planning
Leave room to grow. Choose a recorder with open channels and bays for extra drives. Adding cameras later will shorten retention unless you add storage. If you plan upgrades from 2K to 4K, size storage for the new cameras now.
10. News Context
Retention is what lets you respond to a crime discovered days later. In Sheepshead Bay and Gravesend in March 2026, News 12 reported on video showing home break-ins a few blocks apart. In May 2026, News 12 Long Island reported on a proposed Suffolk County bill concerning businesses preserving and turning over footage; I could not confirm its final status. Whether or not such a law applies to you, having enough storage to preserve footage until someone asks for it is smart planning.
NYPD reported burglary down 19.5% citywide in May 2026 compared with May 2025 (NYPD).
11. Costs
Storage is a small part of a system's cost. Planning ranges in 2026: a surveillance drive of 4 to 8 TB costs roughly $120 to $300; a 12 to 20 TB drive $250 to $550; a recorder with RAID capability $800 to $3,500. Complete installed systems: four cameras $1,600 to $3,600; eight cameras $3,000 to $6,800; sixteen cameras $6,500 to $13,000. These are planning ranges, not quotes.
12. Questions to Ask Your Installer
- How many days of footage will I have at the settings you propose?
- What bitrate are you assuming per camera?
- Is it continuous, motion or mixed recording?
- Do I have RAID or a spare drive?
- How do I add storage later?
- Will you show me the retention on the recorder screen?
See our local pages for commercial camera installation in Brooklyn, home camera installation in Staten Island, business installation in Queens and our services page.
Not sure how much storage you need? Revolvis will walk the property with you and mark the spots.
13. Check Your Existing System
You can often see your retention on the recorder. Look for the playback calendar or storage screen, find the oldest available date and count days to today. If it is shorter than expected, check the number of cameras, bitrate, recording mode and drive health. Sometimes adjusting settings or adding a drive solves the problem cheaply. If the recorder shows errors, back up important footage and call your installer.
14. Common Mistakes
Buying a recorder with a small drive to save money. You pay later in lost footage.
Forgetting margin. Real bitrates exceed estimates at night and in busy scenes.
Counting raw RAID capacity. Usable capacity is lower.
Mixing high and low quality inconsistently. Entrances should be best.
Never testing retention. Check yearly.
Ignoring drive health. A failed drive may stop recording unnoticed.
15. A Quick Reference Table
For a fast estimate, use these approximate totals for continuous recording at 30 days, before margin. They assume 3 Mbps per camera, which is typical for a 4 MP camera with H.265 in moderately busy scenes.
| Cameras | Approximate storage for 30 days |
|---|---|
| 2 | 1.9 TB |
| 4 | 3.9 TB |
| 6 | 5.8 TB |
| 8 | 7.8 TB |
| 12 | 11.7 TB |
| 16 | 15.6 TB |
If your cameras run at 6 Mbps, double these numbers. If you record on motion in quiet areas, your needs may be much lower. Treat the table as a starting point and have your installer confirm with real measurements after the system has run for a few days. A good installer will check the recorder a week after installation to confirm that the projected retention matches reality, and will adjust settings or add a drive if it does not.
More From Revolvis
Cameras are one layer of a secure property. The same in-house crew also handles the rest:
- Keyless entry installation and smart lock installation
- Access control systems and commercial access control
- Video doorbells and intercoms
- Alarm system installation
- Complete unified security
Learn more about Revolvis, meet the team, see all services, browse the blog or contact us.
Areas We Serve
Revolvis installs residential and commercial camera systems across the New York metro area. Every borough and county has its own building stock, rules and wiring challenges, so the plan for a Queens two-family is not the plan for a Manhattan co-op.
- Staten Island: houses, detached garages and shop fronts. See security camera installation in Staten Island.
- Brooklyn: brownstones, row houses and storefronts. See security camera installation in Brooklyn.
- Queens: attached brick homes, two-families and busy commercial strips. See security camera installation in Queens.
- The Bronx: pre-war buildings, bodegas and warehouses. See security camera installation in the Bronx.
- Manhattan: co-ops, condos, offices and retail. See security camera installation in Manhattan.
- Long Island: Nassau County and Suffolk County.
- New Jersey: Jersey City, Newark, Hoboken and nearby towns.
The full list is on the service areas page.
Get a Custom Quote After a Site Visit
Revolvis prices every job after a site visit, because the building sets the cost as much as the equipment does. A few things make the estimate faster and more accurate:
- The address and property type: house, apartment, co-op, condo, storefront or warehouse.
- Which doors, sides and areas you want covered, and what worries you most.
- Photos of those spots and any spots where you already have cabling or power.
- How many days of footage you want to keep and whether you want to watch on your phone.
- Any landlord, board, lender or insurer requirement.
Call 347-258-9165 or use the contact page to book a site visit. The quote you receive is written and itemized, so you can compare it line by line.
Frequently Asked Questions
How do I calculate NVR storage? Multiply cameras by bitrate in Mbps by 10.8 by the number of days to estimate gigabytes. Add margin.
How much storage for 8 cameras for 30 days? At 3 Mbps each with continuous recording, roughly 7.8 TB before margin. Motion recording can reduce this.
Does 4K use more storage? Yes, roughly double 2K at similar settings.
Do I need RAID? For businesses and critical systems, it is a good idea. RAID is not a replacement for backup.
How many days should I keep? Thirty is common. Choose based on your risks and obligations.
Can I add storage later? Often, if the recorder has open bays. Ask before you buy.
Ready for a custom quote? Call Revolvis at 347-258-9165 for a site visit and a written, itemized estimate.
Safety note: A camera system supports, but does not replace, good locks, lighting, alarms and everyday habits. If you are in danger or witnessing a crime, call 911. Prices and legal summaries in this guide are general information for the New York metro area, not an offer or legal advice. A written quote after a site visit governs your actual price, and for legal questions you should confirm with the agencies linked in the article or a licensed attorney.