One frame count, three ways to read it
For non-drop timecode: frames = ((hours × 3,600 + minutes × 60 + seconds) × nominal fps) + frame field. Actual seconds = frames × rate denominator ÷ rate numerator. From seconds, round once to the nearest whole frame.
Worked example
At 23.976 fps (24,000/1,001), 24,000 frames = 00:16:40:00 = exactly 1,001 actual seconds. At 29.97 DF, 00:10:00;00 = 17,982 frames = 599.9994 seconds.
Assumptions and limits
Frame input must be a whole number. Second input can include decimals or a minus sign. Nearest-frame ties round away from zero. Results are frame-aligned; requested seconds can differ by at most half one frame.
For supported rates and input formats, see the frame-rate reference on the calculator home page.