Filmmaking Calculator Questions
Short answers to the math questions that come up on set and in post, each with the formula and a worked example.
Aspect Ratio Questions
What is the best aspect ratio for professional film?
There is no single best ratio. Theatrical features are mostly 2.39:1 (Scope) or 1.85:1 (Flat), the two DCP containers. Television and streaming use a 16:9 (1.78:1) frame, and wider films are letterboxed inside it. Pick for the story and the screen it will play on.
Additional Details: Theatrical: 2.39:1 or 1.85:1. Streaming and TV: a 16:9 frame (3840x2160 or 1920x1080), with the film's own ratio inside it. Social: 4:5 (1080x1350) for the Instagram feed, 9:16 (1080x1920) for Reels, Stories, TikTok and YouTube Shorts. 2.39:1 is often marketed as "21:9", but 21:9 is 2.33:1.
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How do you calculate aspect ratio from resolution?
Divide the width by the height and simplify the fraction. For example, 1920x1080 = 1920÷1080 = 1.78:1, which simplifies to 16:9.
Additional Details: Common calculations: 3840x2160 = 16:9 (4K), 2560x1440 = 16:9 (1440p), 1920x1080 = 16:9 (1080p), 1280x720 = 16:9 (720p).
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What aspect ratio should I use for YouTube?
16:9 is the standard aspect ratio for YouTube videos. This ensures your content displays properly without black bars on desktop and mobile devices.
Additional Details: The YouTube player is 16:9; other ratios are shown with bars. Shorts are vertical, 9:16 (1080x1920). Upload at your master resolution, for example 1920x1080 or 3840x2160.
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Frame Rate Questions
What frame rate should I shoot for slow motion?
For smooth slow motion, shoot at 120fps or higher. 60fps gives 2.5x slow motion when played at 24fps, while 120fps provides 5x slow motion.
Additional Details: Common slow motion frame rates: 60fps (2.5x slower), 120fps (5x slower), 240fps (10x slower), 480fps (20x slower). Higher frame rates require more light and storage.
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What is the difference between 24fps and 30fps?
24fps (or 23.976) is the film standard and gives the familiar cinematic motion. 30fps (in practice 29.97) looks slightly smoother and is the North American TV and online video rate. In 25fps countries, 25 plays the same role.
Additional Details: 24/23.976fps: features, scripted drama. 25fps: broadcast in Europe and other former PAL regions. 29.97/30fps: North American broadcast, web video. 50/59.94/60fps: sports, live events, and footage meant to be slowed down.
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How do you calculate speed percentage for frame rate changes?
Divide your playback frame rate by your shooting frame rate, then multiply by 100. For example: 24fps playback ÷ 60fps shooting = 0.4 × 100 = 40% speed.
Additional Details: Formula: (Playback FPS ÷ Shooting FPS) × 100 = Speed Percentage. This determines how fast or slow your footage will play back.
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Timecode Questions
What is drop frame vs non-drop frame timecode?
Drop frame timecode skips certain timecode numbers so the count keeps pace with real time at 29.97fps. No frames of picture are dropped. Non-drop frame numbers every frame in sequence, so at 29.97fps it runs about 3.6 seconds an hour behind the clock.
Additional Details: Drop frame: matches clock time, the norm for broadcast at 29.97 and 59.94. Non-drop frame: easier to calculate, common for film and post. At 29.97, drop frame skips frame numbers 00 and 01 at the start of every minute except every tenth minute (00 to 03 at 59.94). No picture is dropped, only numbers.
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How do you add timecodes together?
Add each component (hours, minutes, seconds, frames) separately, carrying over when values exceed their limits. 60 seconds = 1 minute, 60 minutes = 1 hour.
Additional Details: Example: 01:23:45:12 + 00:45:30:18 = 02:09:16:05 (assuming 25fps). Remember to account for frame rate limits when adding frames.
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Video Production Questions
How much storage do I need for 4K video?
It depends on the codec's bitrate. 4K H.264 at 50 Mbps uses about 375MB per minute (22.5GB an hour); 4K ProRes 422 at 23.976fps uses about 3.5GB per minute (212GB an hour).
Additional Details: Storage requirements for UHD at 23.976fps: H.264 at 50 Mbps (375MB/min), ProRes 422 (about 3.5GB/min), ProRes 4444 (about 8.0GB/min), per Apple's ProRes white paper. Raw formats vary widely by camera and compression setting.
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What bitrate should I use for streaming?
Use the platform's own figures. For YouTube uploads at 24, 25 or 30fps, YouTube recommends 8 Mbps for 1080p and 35-45 Mbps for 4K. For a YouTube live stream at 1080p60 it recommends 17 Mbps with H.264.
Additional Details: YouTube SDR upload recommendations at 24/25/30fps: 720p 5 Mbps, 1080p 8 Mbps, 1440p 16 Mbps, 2160p 35-45 Mbps. At 48/50/60fps: 7.5, 12, 24 and 53-68 Mbps. Live (H.264): 1080p30 14 Mbps, 1080p60 17 Mbps. Keep a live stream well under your upload speed. Viewers need far less than you upload: Netflix asks for 15 Mbps or more for 4K and 5 Mbps for 1080p, and YouTube recommends 20 Mbps for 4K and 5 Mbps for 1080p. Figures as of October 2026.
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Bitrate & Compression Questions
How do I calculate the right bitrate for my file size limit?
Multiply your target file size in megabytes by 8 to get megabits, then divide by the duration in seconds. For a 500MB file at 10 minutes: (500 × 8) ÷ 600 = 6.67 Mbps.
Additional Details: Formula: Bitrate (Mbps) = (File Size in MB × 8) ÷ Duration in seconds. Remember to account for audio bitrate (typically 128-320 kbps) by subtracting it from your total bitrate budget.
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What is the difference between CBR and VBR encoding?
CBR (Constant Bitrate) maintains the same bitrate throughout, while VBR (Variable Bitrate) adjusts based on content complexity. VBR typically provides better quality for the same average bitrate.
Additional Details: CBR: predictable file size and bandwidth, the usual choice for live streaming. VBR: better quality for the size, with the final size less predictable. 2-pass VBR analyzes the whole file first, so it gets closest to a target size, but takes longer to encode.
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How long will it take to upload my video file?
Multiply your file size in megabytes by 8 to get megabits, divide by your upload speed in megabits per second, then divide by 60 for minutes. A 2GB file at 10 Mbps takes about 27 minutes.
Additional Details: Formula: Upload Time (min) = (File Size in MB × 8) ÷ Upload Speed (Mbps) ÷ 60. Test your actual upload speed at speedtest.net as it's often lower than download speed.
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Resolution & Scaling Questions
How do I scale video without losing quality?
Scale down rather than up wherever you can, use a high-quality scaler such as Lanczos or bicubic, and keep the original aspect ratio so nothing is stretched.
Additional Details: Best practice: Shoot at the highest resolution your camera supports, then scale down for delivery. 4K to 1080p scaling actually improves perceived quality through supersampling.
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What resolution should I export for different platforms?
YouTube/Vimeo: 1080p or 4K. Instagram Feed: 1080x1080 or 1080x1350. Instagram Stories/Reels: 1080x1920. TikTok: 1080x1920. TV/Broadcast: 1080p or 4K depending on specs.
Additional Details: Always check platform guidelines as they change. Higher resolutions look better but take longer to upload and process. Mobile viewers may not notice differences above 1080p.
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What is the difference between 1080p, 2K, and 4K?
1080p (Full HD) is 1920x1080. 2K is approximately 2048x1080 (cinema standard). 4K (Ultra HD) is 3840x2160. 4K has 4× the pixels of 1080p.
Additional Details: DCI 4K (cinema): 4096x2160. UHD 4K (consumer): 3840x2160. Higher resolutions allow for more cropping flexibility in post-production and future-proof your content.
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Need More Help?
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