microSD Recording Days Calculator
A 256 GB high endurance card in a 4K camera recording continuously holds roughly 3.7 days before it overwrites. A standard card, rather than a high endurance one, typically fails within months of continuous writing and often fails silently.
Values update as you change the inputs. Where a figure cannot be computed honestly from what manufacturers publish, this calculator says so rather than showing a zero.
High endurance cards at this capacity
This grid re-orders itself against the number you just calculated, smallest adequate option first.
SanDisk 256GB High Endurance microSD Card with Adapter
$69.99The card most commonly specified by camera makers for continuous recording, and the capacity that gives a single 4K camera roughly a week.
- Capacity
- 256 GB
Prices change often.
SanDisk 128GB High Endurance Video microSDXC Card with Adapter
$36.99Half the capacity at well under half the price, which is enough when the card is a fallback for a network outage rather than the primary store.
- Capacity
- 128 GB
Prices change often.
SanDisk 512GB High Endurance microSD Card with Adapter
$123.99The largest high endurance card here, and the only realistic way to get a fortnight of continuous 4K out of a single camera with no recorder at all.
- Capacity
- 512 GB
Prices change often.
PNY 256GB PRO Elite High Endurance microSDXC Flash Memory Card
$79.99A direct alternative at the same capacity, worth checking when the SanDisk is out of stock.
- Capacity
- 256 GB
Prices change often.
TEAMGROUP High Endurance 256GB microSDXC UHS-I U3 V30, Designed for Monitoring
$59.99A V30 speed rating, which is the class that sustains a 4K write without dropping frames.
- Capacity
- 256 GB
Prices change often.
Integral 128GB High Endurance microSD Card for CCTV and Security Cameras
$38.95Sold specifically for continuous security recording rather than for phones, at the lowest price per gigabyte in this group.
- Capacity
- 128 GB
Prices change often.
The formula
days = (card GB x 1,000 MB x 0.93 usable) / (bitrate Mbps x 450 MB per hour x hours per day)
Card capacity is quoted in decimal gigabytes, and usable space after formatting is a little over 90 percent of it.
Common questions
How many days will a 256GB microSD card record in 4K?
A 256 GB card recording an 8MP, 4K stream continuously at a typical 6 Mbps H.265 bitrate holds roughly 3.7 days before the camera loops back and overwrites the oldest footage. Motion only recording, rather than continuous, stretches that considerably further since the camera then writes far fewer hours of footage across each day.
Why does a microSD card fail faster than a hard drive in a camera?
A standard consumer microSD card is not built for the constant overwrite cycle of continuous security recording, and it typically fails within months under that workload, often silently, so the camera keeps appearing to record after the card has actually stopped writing. A high endurance card, rated specifically for continuous video, holds up far longer under the same workload.
Why is a card usable capacity less than what is printed on it?
Card capacity is marketed in decimal gigabytes, 1,000 MB per GB, and after formatting and file system overhead the usable space works out to roughly 93 percent of that printed figure. That gap is the difference between a card advertised as holding 4 days of footage and one that actually holds closer to 3.7 days in real use.
Does recording only on motion extend microSD card life?
Yes, in two ways. Motion only recording cuts the hours written per day, which directly extends how many days of footage the card holds before overwriting, and it also reduces the total write cycles the card endures over its lifetime, which matters because flash storage of any kind wears out from repeated writes over time.
What resolution setting gets the most days out of a microSD card?
Lower resolution settings, such as 2MP instead of 8MP, use a lower typical bitrate, roughly 2 Mbps against 6 Mbps in H.265, so the same card holds proportionally more days of footage at the lower resolution. The tradeoff is less pixel density for identifying anyone in the recorded footage, so the setting is a genuine quality tradeoff, not a free gain.
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Keep going
A calculated figure is a planning number, not a promise. Every answer here comes from published standards and manufacturer specifications, and real installations vary with light, weather, scene motion and how a camera is actually aimed. Where a figure cannot be computed honestly from what manufacturers publish, this calculator says so rather than showing a zero.
Before you point a camera at anything. Aim at your own property and your own boundary, never into a neighbour's windows. Cameras in bedrooms, bathrooms or anywhere with a reasonable expectation of privacy are a serious legal problem, including for guests and anyone who works in your home. Audio is legally different from video, many US states require the consent of every party to a recorded conversation, and several recorders capture audio by default, so check your own state before enabling it. This is researched general information and not legal advice.