Video Recording Time Calculator
Work out how long you can record for based on your camera, resolution, frame rate and card capacity.
- How long you can record video comes down to two numbers: your card or drive capacity, and your camera's bitrate.
- The quick formula is capacity in GB times 8000, divided by bitrate in Mbps, which gives you seconds of footage.
- There's no single "hours per 128GB" answer for 4K, because bitrate runs anywhere from around 100 Mbps to 2,600 Mbps depending on your codec.
- Capacity isn't the only question. The card also has to be fast enough (V30, V60 or V90) to keep up, or you drop frames.
- The calculator above does all of this across multiple cards at once, with ProRes and RAW presets built in.
Knowing how long you can record video is the difference between a smooth shoot and one of those mistakes that only needs to happen once.
Running out of card halfway through a take, talent mid-line, light perfect, and the camera stops. On a paid shoot with a location booked by the hour, that's not a small thing.
The frustrating part is that it's almost always avoidable. If you've ever run out mid-shoot, the cause usually traces back to a guess about how long you can record video that didn't survive contact with real settings.
Work the numbers out beforehand and the problem disappears. Here's how the maths works, where people trip up, and how to plan a full shoot day without the guesswork.
What Decides How Long You Can Record?
Two things: how much space you have, and how fast your camera fills it.
Space is your card or drive capacity, measured in gigabytes or terabytes.
Speed is your bitrate, the amount of data your camera writes to the card every second while recording.
A higher bitrate means more detail per frame and bigger files, so the same card empties faster.
Everything else, the resolution, the frame rate, the codec, matters only because of how it changes that bitrate.
That's the whole picture. Once you know both numbers, the recording time is fixed. The trick is knowing your real bitrate rather than assuming it.
How Do You Calculate Video Recording Time?
Multiply your capacity in GB by 8000, then divide by your bitrate in Mbps. The result is your recording time in seconds.
The 8000 is there because 1 gigabyte is roughly 8000 megabits, and bitrate is measured in megabits. So a 256GB card shooting 4K at 100 Mbps works out like this:
256 × 8000 ÷ 100 = 20,480 seconds, or about 5 hours 41 minutes.
That's the raw figure. In practice you'll get a little less, because a formatted card never gives you its full labelled capacity and it's sensible to leave headroom.
The same sum underpins the file-size formula card makers use: bitrate divided by 8, times duration, gives you file size.
A Quick Way To Estimate In Your Head
If you don't fancy the full sum on set, here's a shortcut. Every 1 Mbps of bitrate uses about 0.45 GB per hour.
The logic: 1 megabit per second across an hour is 3,600 megabits, and 3,600 divided by 8 is 450 megabytes, which is 0.45 GB. So a 100 Mbps codec burns roughly 45 GB an hour.
A 256GB card at that rate lasts a bit under 6 hours, which lines up with the formula above. Handy for a rough sanity check before you commit to a card count.
Why Isn't There One Simple Answer For 4K?
Because "4K" tells you the resolution, not the bitrate, and bitrate is what fills the card.
Depending on the codec and frame rate, a single 128GB card can hold anywhere from 8 hours of 4K down to under an hour.
Same resolution, same card, wildly different runtime.
A lightly compressed social clip and a high-bitrate cinema file are both "4K", but one sips data and the other floods it.
This is exactly why a generic "hours per card" chart will let you down.
The only number that matters is your camera's actual bitrate in the mode you're shooting, which you'll find in the recording menu.
Mbps or MB/s: What's The Difference?
Bitrate is measured in megabits per second (Mbps). Card write speed is measured in megabytes per second (MB/s).
There are 8 bits in a byte, so you divide bitrate by 8 to compare the two.
This is the single thing that most trips people up. A camera writing 100 Mbps only needs a card sustaining 12.5 MB/s, because 100 divided by 8 is 12.5.
Miss that conversion and you'll either panic-buy a card far quicker than you need, or worse, assume a slow card can handle a fast codec.
Keep the units straight and the rest of the planning falls into place.
Do ProRes and RAW Use More Storage?
Yes, and the jump is bigger than most people expect.
Long-GOP codecs like H.264 and H.265 are built to keep files small, which is why a mirrorless camera can shoot 4K at around 100 Mbps.
Professional acquisition codecs work the other way, preserving quality with far more data.
Apple's own ProRes 422 runs about 147 Mbps at 1080p, and 422 HQ about 220 Mbps, and those figures climb steeply at 4K. RAW formats go higher still, into the thousands of Mbps.
If you're recording ProRes or RAW to an external unit, the storage maths shifts hard in that direction, so plan card and drive capacity around the codec you're actually delivering in.
This is where external recorders earn their place, and it's the same reason storage planning matters so much on Netflix-approved cameras shooting high-bitrate formats.
Will A Bigger Card Also Record Fast Enough?
Not necessarily. Capacity tells you how much you can store. Write speed tells you whether the card can keep up while you record. They're two separate specs, and both have to be right.
That second one is the speed class, the V number printed on the card. V30 guarantees a minimum sustained write of 30 MB/s, V60 sixty, and V90 ninety. As a rough guide:
- V30: standard 4K at everyday bitrates
- V60: higher-bitrate 4K and entry-level 8K
- V90: 8K, high-frame-rate, and heavy RAW work
The word that matters is sustained. Those ratings are the minimum sustained write speed the card holds throughout a long take, not the headline burst speed on the packaging.
If the card can't maintain the rate your camera is writing, you get dropped frames or the recording stops.
Data-recovery labs see this constantly, with lost footage from weddings and events traced back to a card that couldn't sustain the camera's output.
Don't Overspend On Speed You Can't Use
Faster isn't automatically better. A camera shooting 100 Mbps only needs 12.5 MB/s sustained, which a V30 card clears comfortably. Buying a top-tier V90 card for that camera won't improve the footage one bit.
There's a catch in the other direction too. A V90 card in a body that only supports the slower UHS-I bus gets capped at UHS-I speeds regardless of what the card can do.
Match the card to what the camera can actually use, not to the biggest number on the shelf.
How To Plan Card Capacity For A Whole Shoot Day
Working out one card is easy. Planning a full day takes a few more steps, but they're worth it.
- Find your real bitrate. Check the recording menu for the exact mode you're shooting, not a generic figure for the resolution.
- Work out your runtime per card. Use the formula, the mental shortcut, or the calculator above.
- Add headroom. A formatted card gives you less than its label, so plan on using around 90 to 95% of it and leave a margin on top for safety.
- Carry more than one card. Multiple cards let you keep rolling while you offload, and give you a backup if one fails mid-shoot. All storage fails eventually, so a single card is a single point of failure.
- Check the camera's approved list. For demanding modes, some manufacturers publish approved media lists. Worth a look before you buy for 8K or high-frame-rate work.
If you're still deciding on a body, comparisons like the Sony FX3 versus FX6 and FX9 walk through how those figures differ in practice.
What The Calculator Above Does That A Quick Guess Doesn't
A back-of-envelope sum handles one card at one bitrate. A real shoot day rarely stays that tidy, which is where the tool at the top of this page saves you the arithmetic.
It works across multiple cards or drives in one go, so you can see your total runtime for the whole day rather than one card at a time.
The usable-capacity slider defaults to 92%, which quietly builds in the formatting overhead and headroom that catch people out.
And the presets go well beyond basic H.264, down to ProRes, ProRes RAW and ARRIRAW, so the pro codecs that eat storage fastest are covered without you having to look up a single bitrate.
Set your card size, pick your format, and it hands you the timecode. No unit conversions, no mental maths on set.
Before You Hit Record
Recording time isn't a mystery once you know the two numbers behind it.
Capacity and bitrate set the runtime, the speed class keeps the recording stable, and a bit of headroom keeps the surprises out.
Work it out before the shoot, not when the card fills at the worst possible moment.
Sugarland has kept film and TV productions rolling for more than 28 years, family-run since 1997, with kit, studio and crew hire under one roof.
If you're pricing up a shoot and want the camera, recorder and support sorted in one place, take a look at our kit hire range.
Let’s plan your next shoot
Get your equipment, studio and crew all in one place.