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Video Timestamp Calculator

Video & AudioMedia Utilities
Operation

H:MM:SS, MM:SS or seconds; decimals for milliseconds.

Resulting timestamp —
Total seconds
—
Frame number
—
Timecode (HH:MM:SS:FF)
—
Share-link time parameter
—

To add video timestamps, convert each to seconds, combine them, then convert back. 10:00 plus 5:30 is 600 + 330 = 930 seconds, or 00:15:30. At 25 fps that moment is frame 23,250 and timecode 00:15:30:00. The calculator does the same for subtraction and for the gap between two marks.

About this tool

Editors, captioners and people writing chapter lists keep running into the same small sums: where does a scene land after a segment is inserted, how long is the stretch between two markers, which frame is 12:45.5 at 24 fps. This calculator takes timestamps written the way players and editing software show them (H:MM:SS, MM:SS or plain seconds, with decimals for milliseconds) and adds, subtracts or measures the gap. Alongside the clock result it gives total seconds, the frame number at the chosen frame rate, a non-drop timecode and a ?t= value for share links. One limit: timecode for 29.97 and 59.94 fps is counted non-drop, so it will not match drop-frame timecode from a broadcast NTSC timeline.

How to use it

  1. Pick the operation

    Add a duration to a timestamp, subtract one, or measure the gap between two marks.

  2. Type both timestamps

    Use 1:02:03.5, 02:03 or 123 style; minutes and seconds must stay below 60.

  3. Choose the frame rate

    Select the project rate so the frame number and timecode match your timeline.

  4. Read the results

    The resulting timestamp, total seconds, frame, timecode and link parameter update as you type, with the working shown below.

Examples

10:00 plus a 5:30 segment

Operation
Add
First timestamp
00:10:00
Second timestamp or duration
5:30
Frame rate
25 fps (PAL)

Result Resulting timestamp: 00:15:30.000
Total seconds: 930
Frame number: 23,250
Timecode (HH:MM:SS:FF): 00:15:30:00
Share-link time parameter: ?t=930

  1. First = 00:10:00.000 = 600 s; second = 00:05:30.000 = 330 s
  2. Result = 600 + 330 = 930 s
  3. Frame number = floor(930 × 25) = 23250
  4. Timecode = 23250 frames ÷ 25 per labelled second = 00:15:30:00

Inserting a 5 minute 30 second segment at the 10-minute mark moves the next scene to 15:30, which is frame 23,250 at 25 fps.

Chapter gap at 24 fps

Operation
Gap between two
First timestamp
12:45.5
Second timestamp or duration
1:03:10
Frame rate
24 fps (film)

Result Resulting timestamp: 00:50:24.500
Total seconds: 3,024.5
Frame number: 72,588
Timecode (HH:MM:SS:FF): 00:50:24:12
Share-link time parameter: ?t=3024

  1. First = 00:12:45.500 = 765.5 s; second = 01:03:10.000 = 3790 s
  2. Gap = |3790 − 765.5| = 3024.5 s
  3. Frame number = floor(3024.5 × 24) = 72588
  4. Timecode = 72588 frames ÷ 24 per labelled second = 00:50:24:12

From 12:45.5 to 1:03:10 is 50 minutes 24.5 seconds; half a second at 24 fps is frame 12 of that second.

Trim a 45 s intro

Operation
Subtract
First timestamp
00:02:15
Second timestamp or duration
45
Frame rate
30 fps

Result Resulting timestamp: 00:01:30.000
Total seconds: 90
Frame number: 2,700
Timecode (HH:MM:SS:FF): 00:01:30:00
Share-link time parameter: ?t=90

  1. First = 00:02:15.000 = 135 s; second = 00:00:45.000 = 45 s
  2. Result = 135 − 45 = 90 s
  3. Frame number = floor(90 × 30) = 2700
  4. Timecode = 2700 frames ÷ 30 per labelled second = 00:01:30:00

A moment at 2:15 in the original sits at 1:30 once a 45-second intro is cut, frame 2,700 at 30 fps.

How it is calculated

seconds = H × 3600 + M × 60 + S; frame = floor(seconds × fps); FF = frame mod round(fps)

H, M, S
hours, minutes and seconds (with decimals) of a timestamp
fps
frames per second of the project
FF
frame label within the timecode second

Each timestamp is turned into seconds, combined by the chosen operation, and written back as HH:MM:SS.mmm rounded to the millisecond. The frame number counts whole frames elapsed, so a moment partway through a frame belongs to that frame. Timecode divides the frame count by the rounded frame rate, the way non-drop SMPTE timecode labels frames; at whole rates such as 25 fps it matches clock time exactly.

When not to use it

  • Drop-frame NTSC timecode needs a converter that skips frame labels 00 and 01 each minute.
  • Subtitle files with their own offsets are better shifted inside a subtitle editor.
  • Variable frame rate phone footage has no fixed frame number for a given time.

Common mistakes

  • Writing 1:75 for 1 minute 75 seconds; carry it into the minutes as 2:15 instead.
  • Mixing a period for milliseconds with a frame count, so 10.12 means 120 ms, not frame 12.
  • Using the frame rate of the export instead of the source timeline.

Frequently asked questions

Which timestamp formats does it accept?

Hours, minutes and seconds separated by colons (1:02:03), minutes and seconds (2:03), or a plain number of seconds (123). Add a decimal point or comma for fractions of a second, such as 12:45.5. Minutes and seconds after the first field must be below 60.

How is the frame number counted?

It is the number of whole frames that have elapsed: seconds multiplied by the frame rate, rounded down. At 24 fps, 1.5 seconds is frame 36. Many editors number the first frame 0, which matches this count.

Why does my 29.97 fps timeline show a different timecode?

Broadcast NTSC timelines usually use drop-frame timecode, which skips the labels 00 and 01 at the start of most minutes so the timecode tracks the wall clock. This calculator counts non-drop, which runs about 3.6 seconds slow per hour at 29.97 fps.

What is the share-link time parameter?

YouTube and several other platforms start playback partway into a video when the link carries ?t= and a number of whole seconds. The value shown is the result rounded down to the second, so 00:15:30.000 becomes ?t=930.

What happens if a subtraction goes below zero?

A video cannot start before 00:00:00, so the result is set to zero and a warning explains why. Use the gap option if you only want the distance between two marks regardless of order.

Can I add more than two timestamps?

Not in one pass. Add the first two, copy the resulting timestamp into the first box, then add the next one. Each step keeps millisecond precision.

Cite this tool

Using this tool in an assignment, article or report? Copy a citation, or a link for your website.

APA

Tools Directory Editorial Team. (2026, October 25). Video Timestamp Calculator. Tools Directory. Retrieved October 25, 2026, from https://tools.milunir.com/video-audio/media-utilities/video-timestamp-calculator/

MLA

Tools Directory Editorial Team. “Video Timestamp Calculator.” Tools Directory, 25 Oct. 2026, https://tools.milunir.com/video-audio/media-utilities/video-timestamp-calculator/. Accessed 25 Oct. 2026.

Chicago

Tools Directory Editorial Team. “Video Timestamp Calculator.” Tools Directory. Last modified October 25, 2026. Accessed October 25, 2026. https://tools.milunir.com/video-audio/media-utilities/video-timestamp-calculator/.

Link<a href="https://tools.milunir.com/video-audio/media-utilities/video-timestamp-calculator/">Video Timestamp Calculator – Tools Directory</a>