What is SMPTE timecode?

SMPTE timecode is a set of cooperating standards developed by the Society of Motion Picture and Television Engineers to label individual frames of video or audio. It uses the format HH:MM:SS:FF, where FF is the frame count within the current second.

What is drop-frame timecode?

Drop-frame (DF) timecode skips frame numbers 00 and 01 at the start of every minute except every tenth minute, so that the timecode count stays in sync with the real-world clock for 29.97 and 59.94 fps material. It does NOT drop actual video frames — only the frame number labels are skipped.

When should I use 29.97 DF vs 29.97 NDF?

Use 29.97 DF (drop-frame) for broadcast television and anything that must match wall-clock duration exactly, such as commercial spots with strict airtime requirements. Use 29.97 NDF (non-drop) for film-originated content, music videos, and projects where timecode accuracy relative to a specific frame is more important than clock accuracy.

What happens if the result of a subtraction would be negative?

The calculator shows an inline error. SMPTE timecode cannot represent a negative duration; make sure Timecode A is greater than or equal to Timecode B when subtracting.

How accurate is the drop-frame calculation?

The calculator uses the standard SMPTE 12M drop-frame algorithm: frames 00 and 01 are skipped at every minute boundary except multiples of 10 minutes. This is the same logic used in professional NLEs such as Premiere Pro, Avid, and DaVinci Resolve.

Timecode Calculator

Name: Timecode Calculator
Availability: InStock
Author: Nham Vu

Add or subtract SMPTE timecodes (HH:MM:SS:FF) at standard frame rates including 23.976, 24, 25, 29.97 DF, 30, 50, 59.94 DF, and 60 fps.

Frame Rate

Timecode A

Timecode B

Enter two timecodes and press Add or Subtract.

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Summary

Add or subtract SMPTE timecodes (HH:MM:SS:FF) at standard frame rates including 23.976, 24, 25, 29.97 DF, 30, 50, 59.94 DF, and 60 fps.

How it works

Select the frame rate that matches your project (e.g. 29.97 DF for broadcast NTSC).
Enter the first timecode in HH:MM:SS:FF format in the "Timecode A" field.
Enter the second timecode in HH:MM:SS:FF format in the "Timecode B" field.
Click "+" to add or "−" to subtract the two timecodes.
The result appears in HH:MM:SS:FF format along with the equivalent total frame count and wall-clock duration.

Use cases

Calculate the total running time of a sequence by adding clip timecodes.
Find the in-point of a clip by subtracting a duration from an out-point.
Verify edit math when conforming a cut to a locked picture.
Convert between timecode and absolute frame numbers for scripting FFmpeg.
Check drop-frame timecode arithmetic for broadcast deliverables.
Sum multiple segment durations when assembling a programme reel.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu