Time to a zero-based frame index
For a CFR timeline, the estimated picture containing a time is floor(seconds × FPS). Frame zero starts at time zero. At 30 FPS, 2.5 seconds corresponds to index 75: the 76th picture when counted from one. The displayed zero-based convention helps avoid off-by-one errors when comparing an editor, script or dataset.
Frame index back to time
Choose Frame index to timestamp and divide the index by FPS. At 24 FPS, index 48 begins at 2 seconds. Results use HH:MM:SS with six decimal places and also display seconds. This is a plain time conversion, not an SMPTE timecode calculator. Drop-frame label numbering is not implemented.
Enter the source rate deliberately
Presets include 23.976, 24, 25, 29.97, 30, 50, 59.94 and 60. Fractional labels use standard rational rates. FPS is entered by you, not detected. Variable-frame-rate presentation times cannot be recovered from one assumed rate. A browser capture at the calculated time may differ from an exact source-frame index because the decoder handles seeking.
Use the result with extraction
Enter the calculated time in the extractor and inspect the preview before saving. For regular samples, use the entered-FPS interval mode with the same assumption. The first/last tool avoids manual time entry but still needs output inspection. Values are calculated locally without selecting or uploading a video. Frame indexes range from zero to one billion.