How to Calculate Video Duration from Total Frames

Sometimes you have a total frame count (e.g., 145,032 frames) and you need to know exactly how long that is in Hours, Minutes, and Seconds. While automated tools are best, it helps to understand the math behind the scenes.

The Basic Formula

For standard integer frame rates like 24fps or 25fps, the math is simple division.

Step-by-Step Example (25 fps)

Let's convert 3,650 frames at 25 fps into timecode.

1. Find Total Seconds: 3650 / 25 = 146 seconds.
2. Extract Minutes: 146 / 60 = 2 minutes with a remainder of 26 seconds.
3. Result: 00:02:26:00

The NTSC Complexity

Calculating duration for 29.97 fps (Drop Frame) manually is extremely difficult. You cannot simply divide by 29.97 because frame numbers are integers, but the rate is a decimal.

To do this manually, you have to account for the "dropped" frame numbers every minute. This involves a complex algorithm that subtracts 2 frames for every minute passed, adding back frames for every 10th minute.

Using Modulo for Frames

If you are writing code or a spreadsheet formula:

• Frames: Total Frames % Frame Rate
• Seconds: floor(Total Frames / Frame Rate) % 60
• Minutes: floor(Total Frames / (Frame Rate * 60)) % 60
• Hours: floor(Total Frames / (Frame Rate * 3600))