Video & Storage
SD Card Recording Time Calculator
Find out how long you can record on an SD or microSD card at your camera’s bitrate.
Free to useNo sign-up requiredNo watermarkRuns in your browser
Before a wedding, a trip or a day of filming, the question is simple: how much will this card hold? The answer depends on two numbers - the card’s capacity and the bitrate your camera records at - and on remembering that bitrates are in megabits while cards are in gigabytes.
Pick a card size, enter your camera’s bitrate (or choose a typical recording mode as a starting point) and see the recording time in hours and minutes, along with how big each hour of footage will be.
How this tool works
Choose the card size
Tap a common size from 32 GB to 1 TB, or type your own in GB or TB.
Enter the bitrate
Type the figure from your camera’s manual in Mbps or MB/s, or pick a typical recording mode.
Adjust usable space
97% allows for the file system on a freshly formatted card. Lower it if the card already holds files.
Read the result
Recording time, total minutes, and the file size per hour and per minute.
How it works
The usable space is the card’s capacity multiplied by the usable percentage. Cards are labelled in decimal gigabytes (1 GB = 1,000,000,000 bytes), and that is what the calculation uses.
Recording time is the usable space in bits divided by the bitrate: multiply bytes by 8 to get bits, then divide by bits per second. A 128 GB card with 97% usable holds 124.16 GB; at 100 Mbps that is 124.16 × 8 × 1,000 ÷ 100 = 9,933 seconds, or about 2 hours 46 minutes.
If you enter the bitrate in MB/s it is converted at 1 MB/s = 8 Mbps. The typical recording modes are round, mid-range figures - handy for a first estimate, but your camera’s own figure will always be more accurate.
Most cameras record at a variable bitrate, using fewer bits on still or simple scenes, so real recording time is often a little longer than this estimate.
Common use cases
- Deciding how many cards to pack for a wedding, event or holiday.
- Choosing between 128 GB and 256 GB when buying a card for a new camera, drone or action camera.
- Checking whether a single card will last a full conference talk or sports match.
- Comparing how much longer you can record in H.265 than in H.264.
Typical bitrates by recording mode
Round, typical figures for a first estimate. Real cameras vary widely - some record 4K at 50 Mbps, others at 200 Mbps or more - so check your manual or the menu for the mode you use.
| 1080p 30 fps, H.265 (phone-style) | ≈10 Mbps · 4.5 GB/hour |
|---|---|
| 1080p 30 fps, H.264 | ≈17 Mbps · 7.7 GB/hour |
| 1080p 60 fps, H.264 | ≈30 Mbps · 13.5 GB/hour |
| 4K 30 fps, H.265 | ≈50 Mbps · 22.5 GB/hour |
| 4K 30 fps, H.264 | ≈100 Mbps · 45 GB/hour |
| 4K 60 fps, H.264 | ≈150 Mbps · 67.5 GB/hour |
| 4K UHD 29.97p, ProRes 422 HQ (Apple target) | 884 Mbps · 398 GB/hour |
Mbps vs MB/s, and GB vs GiB
Video bitrates are quoted in megabits per second (Mbps, lower-case b). Storage is sold in megabytes and gigabytes (MB, GB, capital B). A byte is 8 bits, so 100 Mbps is 12.5 MB/s, and an hour at 100 Mbps is 45 GB. Mixing the two up gives an answer eight times too big or too small.
Cards and drives are labelled in decimal units: 1 GB = 1,000,000,000 bytes. Windows and some other systems count in binary units (1 GiB = 1,073,741,824 bytes) but still label them “GB”, so a 128 GB card shows as about 119 GB. Nothing is missing - it is the same space counted differently. This calculator uses decimal units throughout.
Formula
Usable space
card capacity × usable %
Recording time (seconds)
usable space (bytes) × 8 ÷ bitrate (bits per second)
File size per hour
bitrate × 3,600 ÷ 8
100 Mbps → 45 GB per hour.
MB/s to Mbps
MB/s × 8
Worked examples
128 GB card, 4K at 100 Mbps
With 97% usable (124.16 GB), 124.16 GB × 8 ÷ 100 Mbps = 9,933 seconds - about 2 hours 46 minutes of recording. Each hour of footage is 45 GB.
64 GB card, a camera that lists 10 MB/s
10 MB/s is 80 Mbps. With the whole card free, 64 GB × 8 ÷ 80 Mbps = 6,400 seconds, or 1 hour 46 minutes. Each hour is 36 GB.
Frequently asked questions
How many hours of 4K video fit on a 128 GB SD card?
At a typical 100 Mbps, about 2 hours 46 minutes with 97% of the card usable. At 50 Mbps (common for H.265) it roughly doubles to about 5 and a half hours. Your camera’s exact bitrate decides it.
Why does my camera say less time than this?
Cameras often estimate conservatively, reserve some space, or split recordings at a clip-length or file-size limit. Some also stop recording when they get too warm. The calculator gives the storage limit, not those camera limits.
Does the card’s speed class affect how much it holds?
No. The speed class (such as V30 or V60) decides whether the card can keep up with the bitrate, not how much fits. A 100 Mbps mode needs a card that sustains at least 12.5 MB/s - V30 or faster is the usual recommendation for 4K.
Why is my 128 GB card shown as 119 GB on my computer?
The card holds 128 billion bytes. Windows counts in binary gigabytes (1,073,741,824 bytes each), which gives about 119. It is the same space in a different unit.
Is anything uploaded?
No. You type numbers, and the calculation runs in your browser.