CCTV Data Storage: How Much Space Your Cameras Need

To size cctv data storage, multiply four things: each camera's bitrate, the hours per day it actually records, the number of cameras, and the number of days you want to keep. A handy shortcut is that 1 Mbps of video recorded around the clock fills about 10.8 GB a day. Add the cameras together, multiply by your retention days, leave some headroom, and you have the drive or card size to aim for. Then, after a week of real recording, check the oldest footage on the timeline, because your scene and settings decide the true figure.

This article is about planning capacity for one or many cameras. If you are weighing a single 4K WiFi camera against your network and memory card, see whether your WiFi and SD card can keep up with a 4K camera. If you are still choosing between cards and a recorder, read whether you need an NVR or an SD card is enough first.

The formula in one line

Storage needed (GB) = bitrate (Mbps) × 0.45 × hours recorded per day × number of cameras × days to keep

Where the 0.45 comes from, so you can trust it:

1. Bitrate is measured in megabits per second. There are 8 bits in a byte, so 1 Mbps is 0.125 megabytes per second.
2. An hour has 3,600 seconds, so 0.125 × 3,600 = 450 MB per hour, which is 0.45 GB.
3. Over 24 hours of continuous recording, that is 10.8 GB per day for every 1 Mbps.

Everything else in this article is about getting honest values for each part of the formula. The bitrate is the one people usually guess wrong, so start there.

Step 1: Find each camera's real bitrate

The bitrate is how much data the camera produces per second for the stream it records. On most models that is the main (high-quality) stream, not the low-quality stream you often see in remote live view.

Three ways to find it, from easiest to most accurate:

• Look in the camera's video settings. Some models show the bitrate, or let you choose it, under a menu such as video settings, image settings or recording settings. Menu names may differ slightly by app version, and some models do not show a bitrate at all.
• Check the manual or the product listing for your exact model. It may list a bitrate range for each resolution. Treat the top of that range as the busy-scene figure.
• Measure it. This is the most reliable method, because it includes your own scene. For a camera recording to a memory card, let the card fill completely, then scroll the playback timeline back to the oldest clip still on it. Card size divided by the number of days covered gives you GB per day. Divide that by 10.8 and you have the average bitrate. For a recorder with a drive that is not yet full, note the free space, wait exactly 24 hours, and note it again; the difference is your GB per day. Once a drive is full and overwriting, the free space stops changing, so use the oldest date on the timeline instead.

Note the measured figure per camera. A camera facing a quiet hallway and one facing a tree-lined street can differ a lot even at the same resolution, because moving leaves, rain and night-time image noise are harder to compress.

Step 2: Decide how many hours per day each camera records

Continuous recording means 24 hours a day. The formula is simple and the result is predictable.

Motion or event recording writes only when something triggers the camera, plus a few seconds before and after on models that support pre-recording. The hours recorded per day then depend on how busy the scene is, which you cannot know in advance. Estimate it like this:

1. Turn on motion recording and leave it for a normal day.
2. Open the event list or the playback timeline and add up roughly how long the recorded blocks cover.
3. Use that number of hours in the formula, then round it up, because some days are busier than others.

A front door on a quiet street might record for a short total each day, while a shop counter might record most of the opening hours. Busy detection settings can make motion recording almost as heavy as continuous recording. If your event list is full of empty clips, fix the detection first; motion detection settings for zones and sensitivity shows how. Fewer false triggers means more days of footage on the same storage.

Some people mix the two: continuous on the most important camera, motion-only on the rest. The formula handles that easily, because you work out each camera separately and then add them up.

Step 3: Multiply by cameras and days, then add headroom

Now put it together:

1. For each camera: bitrate × 0.45 × hours per day = GB per day.
2. Add up all cameras to get the GB per day for the whole system.
3. Multiply by the number of days you want to keep.
4. Add headroom on top, so a busier week, a stormy night or a camera that you later switch to a higher setting does not cut your retention short.

Two more details change the final size:

• Advertised versus usable capacity. Drive and card makers count a gigabyte as 1,000 megabytes, while many recorders and computers count in units that are slightly larger. A drive sold as 2 TB often shows as roughly 1.8 TB on the recorder. The file system and the recorder's own index also take some space.
• Maximum supported size. Cameras accept memory cards only up to a certain size, and recorders accept drives only up to a certain size per bay. Check the label or the manual for your model before buying the largest card or drive in the shop.

Worked examples with stated assumptions

These examples show the method, not what your cameras will do. Bitrates vary by model, settings and scene, so replace them with your own measured figures.

Example A: two cameras at home, recording to memory cards

• Assumptions: each camera averages 2 Mbps, records continuously, and you want a week of footage.
• Per camera per day: 2 × 0.45 × 24 = 21.6 GB.
• Per camera for seven days: about 151 GB.
• Each camera has its own card, so each card needs to hold about 151 GB plus headroom. A 128 GB card would fall short; a larger card would be needed if your model supports one. Switching that camera to motion recording on a quiet scene could make the smaller card enough.

Example B: eight cameras in a small shop, recording to a recorder

• Assumptions: four cameras average 4 Mbps and record continuously; four average 2 Mbps and record on motion for about 8 hours a day. You want two weeks.
• Continuous cameras: 4 × 0.45 × 24 × 4 cameras = 172.8 GB per day.
• Motion cameras: 2 × 0.45 × 8 × 4 cameras = 28.8 GB per day.
• Total: about 202 GB per day, so about 2.8 TB for fourteen days.
• With headroom and the usable-capacity gap, a drive sold as 4 TB is a sensible target. A 3 TB drive would be too tight on a busy week.

Example C: reversing the formula to find retention

If you already own the storage, divide instead: days kept = usable storage (GB) ÷ GB per day. A recorder with about 1,800 GB usable and a system writing 150 GB a day keeps roughly 12 days before loop recording overwrites the oldest footage.

What changes the total the most

When the result is bigger than you hoped, these are the levers to try:

• Resolution. More pixels per frame means more data. Moving from 1080p to a 4K or 8MP setting usually raises the bitrate considerably, although by how much depends on the model and the compression it uses. Use the highest resolution only where you need fine detail, such as an entrance where faces or number plates matter.
• Compression format. Many recent models record in H.265, which typically needs noticeably less data than the older H.264 for similar picture quality. Check your model's video settings to see which one it uses and whether you can switch. If you record to a recorder, make sure it can play back H.265 before changing.
• Frame rate. Fewer images per second means less data, but very low settings can miss the moment a face turns towards the lens.
• Bitrate setting. Where a model lets you cap the bitrate, a lower cap saves space but can make fast motion blocky. Change it in small steps and compare playback clips of the same scene.
• Recording mode. On quiet cameras, switching from continuous to motion-only recording is often the biggest saving of all.
• The scene. Trees, flags, traffic and infrared noise at night all push the bitrate up. Re-aiming a camera so it sees less movement saves storage as well as false alerts.

Change one thing at a time and measure again for a day or two. Otherwise you will not know which change helped.

Check the real retention after setup

The calculation tells you what to buy. The timeline tells you what you actually have. A week or two after setup, once the card or drive has filled and loop recording has started:

1. Open playback for each camera in the app or on the recorder. If you are not sure how to read it, see how to watch playback and save a clip.
2. Step back day by day until the timeline is empty. That earliest day is your real retention for that camera.
3. Compare it with your target. If it is shorter, use the levers above or add storage.
4. Write the number down and check again after any settings change.

Some recorders show an estimated recording time or a free-space figure in their storage menu. Treat it as a guide: it is usually based on current settings and recent activity, so a busier week shortens it. The oldest date on the timeline is the figure that counts.

If the timeline shows fewer days than your storage should hold, or none at all, the problem may be recording itself rather than capacity. Work through why a camera is not recording to its SD card for card setups, or CCTV playback not working on a DVR or NVR for recorders.

Keep stored footage safe

• Use cards and drives made for continuous recording. Look for memory cards labelled for high endurance or video surveillance, and hard drives sold for surveillance use. Ordinary ones are not designed to write all day and tend to wear out sooner.
• Export important clips at once. Loop recording overwrites the oldest footage automatically.
• Keep the clock correct on every camera and recorder, so footage is filed under the right date.

If you need to keep footage for a set period for work or insurance reasons, check local rules and size for that period plus headroom.

When to get help

Ask the seller or a qualified installer when:

• Measured retention is far shorter than the formula predicts even after you have checked the bitrate, recording mode and detection settings.
• A recorder does not detect a new drive, or reports a drive error after you have reseated the cables. Always switch off and unplug the recorder before opening the case.
• You need to run new cables or add a power point for a recorder. Switch off power and use a qualified electrician for any mains wiring, and do not work on high walls or roofs alone on a ladder.
• You are unsure which card or drive size your model supports.

Have ready: the model from each camera label, the app version, the resolution and recording mode of each camera, the storage size, and the oldest date you can see on the timeline.

Install or resell cameras?

Storage problems often only show up weeks after an install, when a customer goes looking for footage that has already been overwritten. A few habits help:

• Ask how long footage must be kept before you quote, and size the storage from that number using the formula, not from the box.
• Measure bitrate on site for one camera at the settings you plan to use, rather than relying on a figure from a different model.
• Write the expected retention on the handover sheet with the settings it assumes, so the customer knows what changes it.
• Come back or call after two weeks to check the oldest date on the timeline against your estimate.
• Show the customer how to export a clip so they do not lose an incident to loop recording.

If you install or sell cameras and want to discuss dealer terms, see the Yoosee dealer program.

Frequently asked questions

How many days of CCTV footage can a 1 TB drive hold?

There is no single answer, because it depends on the total bitrate of every camera writing to it. As a worked example, if the drive shows roughly 900 GB usable and your cameras write 100 GB a day between them, you get about nine days. Swap in your own daily figure, then confirm it from the oldest date on the timeline once the drive is full.

Does recording at night use more storage?

Often it does. Infrared images contain more visual noise, and noise is harder to compress, so the bitrate can rise after dark. Insects near the lens can also trigger extra motion clips. Measuring over a full day and night gives a fairer figure than a daytime test.

Is cloud storage counted in this calculation?

No. The formula covers local storage on a memory card or a recorder. Where a cloud plan is offered for your model and region, it usually stores event clips separately under its own terms, so check the current details in the app rather than assuming it replaces local recording.

Should I buy a bigger drive or lower the resolution?

Start by deciding where detail matters. Keep the higher resolution on cameras covering entrances and lower it, or switch to motion recording, on cameras covering quiet areas. If you still fall short of the days you need, a larger drive is the cleaner fix than lowering quality everywhere.

Why is my real retention shorter than my calculation?

Usually the real bitrate is higher than the figure you planned with, especially at night, or motion recording is triggering far more often than you expected. Check the event list for empty clips caused by trees, shadows or headlights, and re-measure the bitrate over a full day and night.