How to Calculate Filmmaking Math
Step-by-step guides for essential filmmaking calculations. Master the math behind professional video production.
How to Calculate Aspect Ratio
Get Your Resolution
Find the width and height of your video in pixels (e.g., 1920x1080)
Divide Width by Height
Divide the width by the height: 1920 ÷ 1080 = 1.777...
Simplify the Ratio
Convert to standard ratio format: 1.777 = 16:9
Formula
Aspect Ratio = Width ÷ Height
Example
Example: 3840x2160 ÷ = 1.777 = 16:9 (4K UHD)
Common Values
How to Calculate Speed Percentage for Frame Rate Changes
Identify Your Frame Rates
Note your shooting frame rate and playback frame rate
Apply the Formula
Speed % = (Playback FPS ÷ Shooting FPS) × 100
Interpret the Result
Less than 100% = slow motion, more than 100% = fast motion
Formula
Speed % = (Playback FPS ÷ Shooting FPS) × 100
Example
Example: 24fps playback ÷ 120fps shooting = 0.2 × 100 = 20% (5x slower)
Common Values
How to Calculate Target Length Speed Adjustment
Measure Current Length
Get the current duration of your clip in timecode format
Set Target Length
Determine the desired final duration for your clip
Calculate Speed Adjustment
Speed % = (Current Length ÷ Target Length) × 100
Formula
Speed % = (Original Duration ÷ Target Duration) × 100
Example
Example: 2-minute clip to fit 1:30 = (02:00:00 ÷ 01:30:00) × 100 = 133% speed
Common Values
How to Add and Subtract Timecode
Align the Timecodes
Write timecodes in HH:MM:SS:FF format (Hours:Minutes:Seconds:Frames)
Add Each Component
Add frames, seconds, minutes, and hours separately
Handle Carry-Over
Convert excess frames to seconds, seconds to minutes, etc.
Formula
Remember: 25 frames = 1 second (at 25fps), 60 seconds = 1 minute
Example
Example: 01:23:45:12 + 00:45:30:18 = 02:09:16:05 (at 25fps)
Common Values
How to Calculate Target Bitrate
Determine File Size Limit
Know your target file size in MB or GB
Get Runtime Duration
Measure the total runtime of your video
Calculate Required Bitrate
Bitrate (Mbps) = (File Size in MB × 8) ÷ (Runtime in seconds)
Formula
Bitrate (Mbps) = (File Size in MB × 8) ÷ Runtime in seconds
Example
Example: 500MB file, 10 minutes = (500 × 8) ÷ 600 = 6.67 Mbps
Common Values
How to Calculate Upload Time
Check File Size
Get the exact file size in MB or GB
Test Upload Speed
Measure your actual upload speed in Mbps (not download speed)
Calculate Upload Time
Time = (File Size in MB × 8) ÷ (Upload Speed in Mbps) ÷ 60
Formula
Upload Time (minutes) = (File Size in MB × 8) ÷ Upload Speed (Mbps) ÷ 60
Example
Example: 2GB file, 10 Mbps upload = (2000 × 8) ÷ 10 ÷ 60 = 26.7 minutes
Common Values
How to Calculate Recording Time from Storage
Check Available Storage
Find how much storage space you have available in GB
Determine Data Rate
Know your recording format's data rate in MB/min or Mbps
Calculate Recording Time
Time = Available Storage ÷ Data Rate per minute
Formula
Recording Time = Available Storage (MB) ÷ Data Rate (MB/min)
Example
Example: 64GB card, 4K at 400MB/min = 64000 ÷ 400 = 160 minutes (2h 40m)
Common Values
How to Calculate Storage Requirements from Recording Time
Plan Recording Duration
Determine how long you need to record in minutes
Check Format Data Rate
Find your recording format's data rate in MB/min
Calculate Storage Needed
Storage = Recording Time × Data Rate + 20% safety buffer
Formula
Storage Needed = Recording Time (min) × Data Rate (MB/min) × 1.2
Example
Example: 2 hours 4K ProRes = 120 min × 400MB/min × 1.2 = 57.6GB needed
Common Values
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