Video recording time calculator

How much video can you actually fit on a memory card?

Running out of storage halfway through a shoot always happens at the worst moment. Mid-take, on location, no time to swap formats or find a shop that stocks CFexpress cards. The good news: recording time is entirely predictable once you know two numbers. How much storage you have, and how fast your camera is writing data to it.

Use the calculator above to get an exact figure for your setup. Below, we break down how the maths works, how much footage different formats actually produce, and how to plan storage for a full shoot day, not just a single card.

How recording time is calculated

Every video format writes data at a certain rate, measured in megabits per second (Mbps). Higher bitrate means better image quality, and a faster-filling card. The formula is simple:

Recording time = (storage capacity × 8000) ÷ bitrate

The 8000 converts gigabytes into megabits (1 GB ≈ 8000 Mb). So a 256GB card recording at 100 Mbps, a typical 4K H.264 setting, gives you roughly:

(256 × 8000) ÷ 100 = 20,480 seconds ≈ 5 hours 41 minutes

In practice, you'll get a bit less than that. Cards and drives reserve space for file systems, metadata and formatting overhead, usually 5 to 10% of the advertised capacity. That's why the calculator includes a usable capacity adjustment rather than assuming you get every gigabyte on the label.

Recording time by format

Bitrate varies enormously depending on codec, resolution and frame rate. Here's roughly what to expect from common formats at 4K, based on a 256GB card with 92% usable capacity:

The gap between H.264 and RAW formats is enormous. The same card that holds over 5 hours of compressed 4K footage might hold barely 12 minutes of ARRIRAW. This is the most common miscalculation people make when planning storage for a shoot: budgeting card count based on a codec they're not actually going to shoot in.

How many cards do you actually need?

Once you know your recording time per card, the real question is how that maps onto a shoot day. Most productions aren't recording continuously. A typical shoot day involves far more setup, blocking and resets than actual rolling time. As a rough planning figure, 2 to 4 hours of actual recorded footage across an 8 to 10 hour shoot day is common for scripted or commercial work, though documentary and run-and-gun styles can run much higher.

Multiply your expected recorded hours per day by the number of shoot days, then divide by your per-card recording time to get a card count. Always add at least one spare. Cards fail, fill faster than expected on high-action days, or need to come out for offloading while a second card keeps rolling.

Capacity isn't the only number that matters

It's easy to focus purely on gigabytes, but write speed matters just as much, especially at higher bitrates. A card can have huge capacity and still be the wrong choice if it can't sustain the write speed your format demands. ProRes RAW and ARRIRAW in particular need cards or SSDs rated for sustained high-speed writes, typically V90 SD cards or CFexpress Type A/B, not just fast enough for photos. Recording above a card's sustained write speed usually causes dropped frames or a hard stop, no matter how much free space is left.

The table below shows minimum sustained write speeds for common card and media types, so you can match the right card to your format before it becomes a problem on set.

Worth checking against your specific camera's spec sheet before a shoot, particularly if you're stepping up in resolution or frame rate from what you're used to.

Quick answers

How much video can a 256GB card hold?

Around 5 hours at 4K H.264, or about 45 minutes at ProRes 422 HQ. Slow motion (60fps and up) and RAW formats cut that dramatically. Use the calculator above with your specific format for an exact figure.

Why does ProRes take up so much more space than H.264?

H.264 and H.265 are compressed, lossy codecs designed to shrink file size while keeping visual quality high. ProRes and RAW formats prioritise image data and post-production flexibility over file size, which means significantly higher bitrates and much shorter recording times per gigabyte.

Does higher frame rate always mean more storage used?

Yes. Doubling your frame rate, say from 30fps to 60fps, roughly doubles your bitrate and halves your recording time, since the camera is capturing and storing twice as many frames per second.

How much free space should I leave on a card?

Plan around 90 to 95% usable capacity rather than the full advertised number. Most cards report their capacity slightly optimistically once formatted, and file systems reserve some space for metadata.

Can bitrate change during a shoot?

For variable bitrate codecs like H.264 and H.265, yes — busier, more detailed scenes push bitrate higher, which slightly reduces actual recording time versus the average figure. Fixed-rate formats like ProRes and RAW don't vary, so their recording time is far more predictable.

How many GB is 1 hour of 4K video?

Roughly 45GB per hour at a typical 100 Mbps 4K H.264 setting. Higher frame rates, ProRes, or RAW push this several times higher — see the format table above for exact figures.

Is 256GB enough for 4K video?

For most run-and-gun or single-day shoots, yes — around 5 hours at standard 4K H.264. For multi-day shoots, high frame rate work, or ProRes/RAW, you'll want considerably more capacity or several cards.

How long will a 64GB SD card record 4K?

About 1 hour 25 minutes at a standard 100 Mbps 4K H.264 bitrate, less at higher frame rates or bitrates.

How long is 128GB of 1080p video?

Around 5 hours at a typical 1080p bitrate of 50 Mbps. Lower-bitrate compression settings will stretch that further.

How much video time is 32GB?

About 43 minutes at 4K H.264 (100 Mbps), or closer to 1 hour 25 minutes at 1080p. RAW formats would fill it in a few minutes.

How long will 2TB record 4K?

Roughly 44 hours at standard 100 Mbps 4K H.264 — enough for several shoot days of continuous rolling, though real-world usage is usually well under that per day.

Which is better, 1TB or 256GB?

Depends on your shoot length and format. 1TB gives roughly 4x the runtime of a 256GB card, useful for long documentary days, high frame rate work, or ProRes/RAW. For short scripted setups with regular offloading, multiple 256GB cards often give more flexibility than one large card.

Need the cards, drives or cameras to match your next shoot? Browse our equipment or request a quote and we'll help you plan storage alongside the rest of your kit.