BYTETOOLS

SMPTE Timecode Calculator

Convert between SMPTE timecode and frame numbers at 23.976 to 60 fps, with true drop-frame arithmetic, plus add and subtract two timecodes.

Drop-frame timecode is written with a semicolon before the frames (00:01:00;02).

Timecode to frames

107,892
Frame number
00:59:59.996
Real running time
3599.996 s
Total seconds

Frames to timecode

01:00:00;00
Timecode
00:59:59.996
Real running time
3599.996 s
Total seconds

Add or subtract timecodes

00:02:15;14
Result
4,060
Result in frames
00:02:15.469
Real running time

Why drop-frame exists

NTSC video runs at 30000/1001 = 29.97 fps, but timecode counts 30 frame numbers per second. Counting non-drop, one hour of timecode takes 108,000 frames, which is 3603.6 real seconds — the clock drifts 3.6 seconds ahead every hour. Drop-frame skips frame numbers 00 and 01 at the start of every minute except every tenth, so an hour is 107,892 frames and lands within 3.6 milliseconds of real time. No actual video frames are ever discarded; only the labels are.

What is the SMPTE Timecode Calculator?

The ByteTools SMPTE Timecode Calculator converts a timecode to a frame number, a frame number back to timecode, and adds or subtracts two timecodes — at 23.

  • Eight frame rates from 23.976 to 60 fps
  • True drop-frame arithmetic at 29.97 and 59.94, in both directions
  • Rejects impossible drop-frame timecodes instead of accepting them silently
  • Real running time shown alongside every result
  • Add or subtract two timecodes, including negative results
  • Pure calculation — instant, no file needed and nothing uploaded

How to use the SMPTE Timecode Calculator

  1. 1

    Pick your project's frame rate and tick or untick drop-frame counting.

  2. 2

    Type a timecode as HH:MM:SS:FF to see its frame number and real running time.

  3. 3

    Type a frame number to get the timecode back, or use the Send to buttons to move a value between the boxes.

  4. 4

    Enter two timecodes in the add and subtract section and choose the operation.

  5. 5

    Copy any result with the buttons beside it.

About the SMPTE Timecode Calculator

The ByteTools SMPTE Timecode Calculator converts a timecode to a frame number, a frame number back to timecode, and adds or subtracts two timecodes — at 23.976, 24, 25, 29.97, 30, 50, 59.94 and 60 fps. Every result also shows the real running time, which is where non-integer frame rates get interesting.

Drop-frame counting is implemented properly, not approximated. At 29.97 fps the frame numbers 00 and 01 are skipped at the start of every minute except every tenth, so an hour of timecode is 107,892 frames rather than 108,000. The tool uses that arithmetic in both directions and rejects timecodes like 00:01:00;00 that can never exist, instead of silently accepting them.

This is a pure calculator, so it runs instantly in your browser with no file, no upload and no media engine to download. It follows SMPTE ST 12-1 timecode counting; the conversions round-trip exactly across a full 24 hours at every supported frame rate.

Frequently asked questions

What is drop-frame timecode?

It is a counting trick for 29.97 fps video. The labels 00 and 01 are skipped at the start of every minute except every tenth, so the timecode clock keeps pace with real time. No actual video frames are ever discarded — only the numbers used to name them.

What is the difference between 29.97 drop frame and non-drop frame?

Non-drop counts every frame number in order, so after an hour the timecode reads 3.6 seconds ahead of the wall clock. Drop-frame skips 108 labels an hour to compensate, landing within about four milliseconds of real time.

How many frames are in an hour of 29.97 fps video?

107,892 frames, which is what drop-frame timecode counts to reach 01:00:00;00. Non-drop timecode reaches 01:00:00:00 after 108,000 frames, but by then 3.6 seconds more real time has actually passed.

Why is my timecode rejected as invalid?

In drop-frame mode, frame numbers 00 and 01 do not exist at the start of most minutes, so a timecode like 00:03:00;01 can never occur. The tool tells you rather than quietly converting a value your edit system would refuse.

Does drop-frame timecode apply to 24 or 25 fps?

No. Drop-frame only exists to correct the 1000/1001 slowdown in NTSC rates, so it applies to 29.97 and 59.94 fps. At 24, 25, 30, 50 and 60 fps the timecode already matches real time and the setting is ignored here.

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