Timecode Calculator

About the Timecode Calculator

Video and film editors label every frame with SMPTE timecode in the form HH:MM:SS:FF: hours, minutes, seconds and frames. Timecode makes it possible to log shots, sync sound and pictures, and calculate durations precisely. Because the last field counts frames, not hundredths of a second, adding or subtracting timecode by hand needs care, and drop-frame timecode at 29.97 fps adds another layer of complexity.

This timecode calculator adds and subtracts timecodes, converts timecode to a frame count and frames back to timecode at the common frame rates: 23.976, 24, 25, 29.97 drop-frame and non-drop, 30, 50, 59.94 drop-frame and non-drop, and 60. It also shows how much real time the result represents.

How to Use the Timecode Calculator

Choose the frame rate of your project.

Choose the operation: add two timecodes, subtract the second from the first, convert a timecode to frames, or convert a frame count to timecode.

Enter the timecodes as HH:MM:SS:FF. Drop-frame timecode is often written with a semicolon before the frames, as in 01:00:00;00; either separator is accepted.

The Formulas

  non-drop:   frames = (h × 3600 + m × 60 + s) × fps + f
  drop-frame: frames = (h × 3600 + m × 60 + s) × nominal fps + f − d × (total minutes − ⌊total minutes / 10⌋)
              d = 2 at 29.97, 4 at 59.94; nominal fps = 30 or 60
  real time:  frames ÷ actual fps   (29.97 = 30000/1001, 23.976 = 24000/1001)

Step-by-Step Example

Add 00:10:30:12 to 01:00:00:00 at 24 fps.

  01:00:00:00 = 3,600 s × 24 = 86,400 frames
  00:10:30:12 = 630 s × 24 + 12 = 15,132 frames
  total = 101,532 frames
  101,532 ÷ 24 = 4,230 s remainder 12 → 01:10:30:12
  real time: 1 h 10 min 30.5 s

Drop-Frame Timecode Explained

NTSC colour video runs at 30000/1001 frames per second, about 29.97, not 30. If timecode simply counted 30 frames per second, the label would fall behind the clock by 3.6 seconds every hour, about 86 seconds a day, which matters for broadcast schedules.

Drop-frame timecode fixes this by skipping two frame numbers, 00 and 01, at the start of every minute, except minutes 00, 10, 20, 30, 40 and 50. That removes 108 numbers an hour, exactly enough to keep the timecode within a few milliseconds of the clock. No picture is lost; only labels are skipped. So after 00:00:59;29 the next frame is 00:01:00;02, and a timecode such as 00:01:00;00 does not exist. The calculator rejects such impossible values.

At 59.94 fps the same scheme skips four frame numbers per minute. An hour of 29.97 drop-frame timecode is 107,892 frames; an hour of 29.97 non-drop timecode is 108,000 frames and takes about 1 hour 3.6 seconds of real time.

Choosing the Right Frame Rate

The frame rate must match the project or the source media. Film and many streaming productions use 23.976 or 24 fps. PAL regions use 25 or 50 fps, where timecode and real time match exactly. NTSC broadcast uses 29.97 or 59.94, usually drop-frame when running time must match the clock, and non-drop for some post-production workflows. Mixing rates, such as adding a 25 fps duration to a 24 fps timecode, gives meaningless results; convert to real time first.

Timecode Arithmetic in Practice

Editors add timecode to work out the end of a clip from its start and duration, subtract to find the duration between in and out points, and convert to frames for effects and audio tools that count samples or frames. The calculator works in frames internally, then converts back, which avoids the base-60 and base-24 carrying mistakes that are easy to make by hand. Negative results from subtraction are shown with a minus sign, which usually means the timecodes were entered in the wrong order.

Timecode Beyond 24 Hours

Many systems wrap timecode at 24 hours, back to 00:00:00:00. The calculator keeps counting into hours above 23, so long recordings and sums of many clips stay readable. Broadcast workflows also often start programmes at 01:00:00:00 or 10:00:00:00 rather than zero, leaving room for bars, tone and countdown leaders before the programme; subtract the start timecode to find the running time.

Frames, Fields and Audio Samples

Interlaced video splits each frame into two fields, so 29.97 fps interlaced material has 59.94 fields per second, but timecode still counts frames. Audio is measured in samples, commonly 48,000 per second for video work, giving 2,000 samples per frame at 24 fps and 1,601.6 samples per frame at 29.97 fps. That fractional figure is why audio and video at NTSC rates repeat their alignment only every five frames, a detail that matters when syncing sound by sample count.

Quick Reference

At 24 fps, one second is 24 frames, one minute 1,440 and one hour 86,400. At 25 fps an hour is 90,000 frames, and at 30 fps non-drop it is 108,000.

Understanding Your Result

The headline gives the resulting timecode.

The frames line gives the total number of frames at the chosen rate.

The real time line converts the frames to actual running time using the true frame rate.

The inputs line shows each input timecode and its frame count.

When Should You Use This Calculator?

Use it to add durations to a start timecode or find the length between two timecodes.

Use it to convert between timecode and frame counts for effects or audio.

Use it to check drop-frame timecode and its real running time.

Common Mistakes

Treating frames as hundredths. 00:00:01:12 at 24 fps is 1.5 seconds, not 1.12.

Using the wrong frame rate. Results only make sense at the project's rate.

Typing impossible drop-frame values. Frames 00 and 01 do not exist at most minute starts.

Assuming 29.97 non-drop matches the clock. It drifts 3.6 seconds per hour.