Why does drop-frame timecode use a semicolon?

A semicolon before the frame field is the common visual convention for identifying drop-frame timecode, such as 01:00:00;00. This calculator always formats drop-frame results with a semicolon.

Are 23.976 and 29.97 exact frame rates?

The calculator uses the exact rational rates 24000/1001 and 30000/1001 frames per second. The decimal names 23.976 and 29.97 are conventional rounded labels.

Can timecode subtraction produce a negative result?

Yes. Negative arithmetic and frame counts are supported. The result is shown with a leading minus sign, and a separate positive 24-hour wrapped clock value is also provided.

Does this calculator upload project timecodes?

No. Parsing, calculation, copying, and formatting all happen locally in the browser, and input values are not sent to a backend.

Timecode Calculator — Add, Subtract & Convert Frames

Calculate with production timecode at common whole and NTSC-compatible frame rates. Add or subtract two timecodes, convert a timecode to its signed frame count, or turn frames back into a normalized timecode label.

Calculation inputs

Project frame rate and counting mode

DF means drop-frame; NDF means non-drop-frame. Match the timeline or device setting exactly.

Calculation

First timecode

Format: HH:MM:SS;FF for drop-frame or HH:MM:SS:FF for non-drop-frame.

Timecode to add

Use a leading minus sign if the offset itself is negative.

Your timecodes stay on this device. Inputs are not uploaded, stored, or included in analytics events.

Result

Result timecode 01:10:00;00

Total frames125,874

Elapsed duration01:09:59.996

24-hour clock01:10:00;00

Rate used29.97 DF

The two timecodes are converted to frame counts, added exactly, and formatted back at 29.97 drop-frame.

How to use this timecode calculator

Match the project rate. Check the timeline, recorder, camera, or delivery specification. At 29.97 and 59.94, also match DF or NDF.
Choose the operation. Add an offset, subtract an in-point from an out-point, convert one timecode to frames, or convert a signed frame count to timecode.
Enter timecode in four fields. Use HH:MM:SS:FF for NDF. In DF modes, either separator is accepted on input and the normalized result uses HH:MM:SS;FF.
Review every representation. The main result is timecode, while the supporting values show the signed frame count, exact elapsed duration at the media rate, and the clock value after a 24-hour wrap.

Hours may exceed 23 for duration-style calculations. A leading minus sign is accepted for negative timecodes and frame counts.

Timecode and total-frame formulas

Non-drop-frame timecode is an integer label count. If N is the nominal timebase—24, 25, 30, 48, 50, or 60—then:

total frames = ((hours × 3600 + minutes × 60 + seconds) × N) + frames

Addition and subtraction are performed on these total frame counts. The result is then divided back into hours, minutes, seconds, and frames. This avoids carrying frames and seconds by hand and keeps arithmetic exact.

Elapsed duration is a separate concept from the label. It is calculated from the exact media rate:

elapsed seconds = total frames ÷ exact frames per second

For example, this page uses 24000/1001, 30000/1001, and 60000/1001 for the fractional rates conventionally labelled 23.976, 29.97, and 59.94. It does not substitute rounded decimal math.

How 29.97 and 59.94 drop-frame counting works

Drop-frame timecode drops numbers, not video frames. At a nominal 30-frame timebase, labels ;00 and ;01 are skipped at the start of every minute except each tenth minute. At a nominal 60-frame timebase, labels ;00 through ;03 are skipped on the same minute pattern.

dropped labels = D × (total minutes − floor(total minutes ÷ 10))

Here, D is 2 for 29.97 DF and 4 for 59.94 DF. The calculator rejects impossible labels such as 00:01:00;00 at 29.97 DF, then explains the first valid label for that minute. A semicolon in the formatted output makes the counting mode visible.

Technical references: SMPTE ST 12-1 — Time and Control Code, Apple QuickTime — Timecode Media Handler Functions, and Apple Professional Video Applications — Timing Attributes.

Timecode conversion examples

Rate and mode	Input	Total frames	Elapsed duration	What it shows
24 fps NDF	`01:00:00:00`	86,400	01:00:00.000	Whole-rate timecode and clock time align exactly.
23.976 NDF	`01:00:00:00`	86,400	01:00:03.600	The 24-base label count runs slower than wall-clock time.
29.97 NDF	`01:00:00:00`	108,000	01:00:03.600	Every nominal 30-base label is retained.
29.97 DF	`01:00:00;00`	107,892	00:59:59.996	108 labels have been skipped during the hour.
59.94 DF	`00:10:00;00`	35,964	00:09:59.999	Drop-frame counting closely follows clock time.

Assumptions and limits

This is a frame-label calculator, not a media-file inspector. It assumes a constant selected frame rate and does not read variable-frame-rate timestamps, clip metadata, edit decision lists, user bits, field-pair timecode, pull-up/pull-down state, or a device’s jam-sync status. Confirm the actual timeline rate and DF/NDF mode before using a result in a conform, broadcast delivery, or recorder setup.

Timecode calculator FAQ

How do I add two timecodes?

Choose the project rate, select Add timecodes, and enter both values. The calculator converts each value to a signed integer frame count before adding, so frame and second carries are handled automatically.

How do I find a clip duration from in and out timecodes?

Select Subtract timecodes, enter the out-point first, and enter the in-point second. The result is out − in. Whether an out-point is inclusive or exclusive is a workflow convention; add one frame if your required duration includes both endpoint frames.

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

DF skips selected label numbers to keep fractional-rate timecode close to clock time. NDF counts every nominal label. Neither option changes or removes the underlying video frames.

Why is 00:01:00;00 invalid at 29.97 DF?

At minute 1, the ;00 and ;01 labels are omitted. The sequence advances from 00:00:59;29 to 00:01:00;02. Minute 10 starts at 00:10:00;00 because tenth minutes do not omit labels.

Does timecode always wrap at 24 hours?

Many timecode systems use a 24-hour clock, while duration calculations often need extended hours. This calculator keeps the signed unwrapped result as the main value and also shows its normalized 24-hour clock representation.

Are my production timecodes uploaded?

No. The page performs calculations and copying in the browser. It does not send entered timecodes or frame counts to a backend.