Working on films today requires a surprising amount of number crunching. We have become adept at a wide range of conversions -- but only with the use of the right software or calculator. Unfortunately, there are going to be times when the computer is unavailable or the special timecode calculator is on the fritz. Do you know how to convert film feet/frames to timecode, or how to convert non-drop frame code to drop frame?

Here are some formulas that I have compiled over the years. Some came from such sources as Music Editing for Motion Pictures by Milton Lustig (1980); others were taught to me by the late New York film editor Irving Oshman. The rest, well, I figured out.

So file them away in your editing kit. You never know when the next energy crisis will hit, and you'll have to do your cipherin' the old-fashioned way.

Multiply 16mm footage by 2.5

Example: Convert 36 16mm feet to 35mm

36 x 2.5 = 90 35mm feet

Multiply 35mm footage by 0.4

Example: Convert 90 35mm feet to 16mm

90 x 0.4 = 36 16mm feet

One 35mm frame = 0.0625 feet (16 frames per foot).

Multiply the frames part by .0625 to get their decimal equivalent. Or make a little chart of 35mm frame decimal equivalents:

1 = 0.0625 9 = 0.5625
2 = 0.1250 10 = 0.6250
3 = 0.1875 11 = 0.6875
4 = 0.25 12 = 0.75
5 = 0.3125 13 = 0.8125
6 = 0.3750 14 = 0.8750
7 = 0.4375 15 = 0.9375
8 = 0.5 16 = 1

Example: Add 39+14 to 1769+07

Use the chart to find the decimal equivalent of 14 frames: .8750
On a regular calculator, enter 39.8750 and press +
Look up the decimal equivalent of 07 frames: .4375
Enter 1769.4375 and press =
The result is 1809.3125
Look up the frame equivalent of .3125: 5 frames

The answer is 1809+05

The 16mm decimal equivalent of one frame is .025 feet (40 frames per foot). Using that value, you can create a 16mm frame-equivalent chart similar to the one above and do 16mm calculations the same way.

Example: Convert 16mm 83+38 to its 35mm equivalent.

Multiply 38 frames by .025 to get .95
Multiply 83.95 by 2.5 to get 209.875
Look up the 35 mm frame equivalent of .875, or divide .875 by .0625 to get 14

 The answer is 209+14

  1. Add 1 frame to the LFOA (Last Frame of Action).
  2. Subtract 12 from the footage.

Example: How long is a reel of 35mm film whose LFOA is 1827+13?

Add 1 to the frame count:
13 + 1 = 14
Subtract 12 from the footage: 1827 - 12 = 1815

 The answer is 1815+14

Note for sound editors: this is also the insert start mark of the reel.

  1. Multiply film frames by 1.25
  2. Drop fractional frame value (see #9 below).

Example 1: Convert 4 film frames to video frames

4 x 1.25 = 5
The answer is 4 film frames = 5 video frames

Example 2: Convert 7 film frames to video frames

7 x 1.25 = 8.75
Dropping the fraction, the answer is 8 video frames.

  1. Multiply video frames by 0.8
  2. Drop any fractional value (see #9 below).

Example 1: Convert 5 video frames to film frames

5 x .8 = 4
The answer is 5 video frames = 4 film frames

Example 2: Convert 7 video frames to film frames

7 x .8 = 5.6
The answer is 5 film frames

When converting between film and video, sound editing systems and dubbing controllers typically truncate fractional frame values (that is, they drop the fraction). This means that the system picks the video or film frame that contains the leading edge of the frame being converted. Film systems and Avid film systems follow the 3:2 telecine cadence and pick the nearest whole frame, which means that fractional values are rounded. (Values of less than .5 are truncated, values of .5 and above are adjusted up to the nearest whole frame.)

Quick conversion -- good for short lengths:

  1. Divide feet by 3, multiply quotient by 2 to get seconds.
  2. Multiply any remainder by 16 to get frames.
  3. Add the rest of the frames and divide by 6 to get quarter-seconds.

Example: Convert 19+03 to time

19 / 3 = 6 (with 1 foot left over)
6 x 2 = 12 seconds
1 foot x 16 = 16 frames
16 frames + 03 frames = 19 frames
19 / 6 = approximately 3 quarter-seconds

The answer is 19+03 = 12 3/4 seconds

Standard conversion -- good for all lengths:

  1. Multiply 35mm feet by 16 to convert to total frames (multiply 16mm feet by 40).
  2. Add frames to (a) to get total frames.
  3. Divide by 1440 to get total minutes (1440 frames per minute).
  4. Multiply the answer by 60 to get seconds. Round off as needed.

Example: Convert 1240+13 to real time.

1240 x 16 = 19840 frames
19840 + 13 = 19853 total frames
19853 / 1440 = 13.7868 minutes
.7868 x 60 = 47.2083 seconds

 The answer is 13 minutes and 47 seconds

  1. Convert feet + frames to total film frames (multiply feet by 16 and add any additional frames).
  2. Multiply by 1.25 to get total video frames.
  3. Divide by 108,000 to get total hours (60 minutes x 60 seconds x 30 frames = 108,000 video frames in one hour).
  4. Divide remainder of (c) by 1,800 to get total minutes (60 minutes x 30 frames = 1,800 frames in one minute)
  5. Divide remainder of (d) by 30 to get seconds.
  6. Remainder of (e) is frames. (Truncate fractional values for sound editorial, round them for picture editorial. See #9, above.)

Example: Convert 357+08 to 30-fps timecode.

357 x 16 = 5712
5712 + 8 = 5720 total film frames
5720 x 1.25 = 7150 total video frames
7150 / 108,000 = 0 hours with a remainder of 7,150 frames
7150 / 1,800 = 3 minutes with a remainder of 1,750 frames
1750 / 30 = 58 seconds with a remainder of 10 frames

 The answer is 00:03:58:10

Drop frame timecode adds 2 frames every minute, but not when the minute ends in 0 (minute 10, 20, 30, etc.).

  1. Ignore hours.
  2. Multiply minutes by 2
  3. Take the left-most integer of the original minutes column and multiply by 2.
  4. Subtract (c) from (b).
  5. Add the result, in frames, to the non-drop frame value.
  6. Convert frames to seconds, as needed (30 frames = 1 second).

Example: Convert 07:32:56:27 non-drop to drop frame timecode

Double the minutes: 32 x 2 = 64
Double the left-most minutes integer: 3 x 2 = 6
Subtract: 64 - 6 = 58
Add the result to the frames column: 27 + 58 = 85
Convert to seconds: 85 / 30 = 2 with a remainder of 25, or 2 seconds 25 frames.

 The answer is 07;32;58;25

  1. Ignore the hours column.
  2. Double the minutes column.
  3. Double the left-most integer of the minutes column.
  4. Subtract that from the doubled minutes.
  5. Continue as in #12, but subtract from the frames column.

  1. If the hour is used as a reel number, then ignore hours.
    If not, multiply hours by 86,400 to get total film frames.
    (90 feet per minutes x 60 minutes per hour x 16 film frames per foot = 86,400).
  2. Multiply the minutes column by 1,440 to get total film frames.
    (90 ft. per min. x 16 film fr. per foot = 1,440).
  3. Multiply seconds by 24
    (24 film frames per second).
  4. Convert video frames to film frames.
  5. Add (b), (c) and (d), or add (a), (b), (c) and (d), as appropriate, to get total film frames.
  6. There are 16 film frames per foot. Convert to feet and frames, as needed.

Example: Convert 02:03:59:10 to 35mm feet and frames
(assume the hour represents a reel number)

Ignore hours
3 x 1,440 = 4,320
59 x 24 = 1,416
10 video frames x .8 = 8
4,320 + 1,416 + 8 = 5,744 film frames
5,744 / 16 = 359

 The answer is 359+00

  1. First convert to non-drop frame (see #13 above).
  2. Then use the formula outlined in number 14 to convert to feet/frames.

  1. Divide the non-standard film speed by 24.
  2. Use the AudioSuite "Time Compression Expansion" module.
    Enter the value from (a) into the "ratio" box to create an audio file that will run in sync with corrected pitch.

Example: Picture was shot at 12 fps, but audio was recorded at 24 fps. By how much do you have to change the speed of the audio to match the picture?

Target rate divided by original rate = conversion rate
12 / 24 = .5
Enter .5 as the "ratio" in AudioSuite's Time Compression Expansion module.

  1. Divide 24 by the non-standard speed (opposite of #16).
  2. Use the AudioSuite "Pitch Shift" module.
    Enter the value from (a) into the "ratio" box and deselect "Time Correction."

Example: same as #16 above. Picture was shot at 12 fps, but audio was recorded at 24 fps. By how much do you have to change the pitch to match the length with the appropriate pitch change?

24 / 12 = 2.0
Enter 2.0 in the ratio box in AudioSuite's "Pitch Shift" module to render the audio file as the equivalent of 12 fps with its pitch raised accordingly.


1 film frame @ 24 fps = 2000 audio samples at 48 kHz
1 film frame @ 24 fps = 1837.5 audio samples at 44.1 kHz

1 second @ 24 fps = 0.6 of a foot in 16mm = 1.5 feet in 35mm
1 minute @ 24 fps = 36 feet in 16mm = 90 feet in 35mm

1 film frame = 1.25 video frames
1 video frame = 0.8 film frames

1 hour real time = 00:59:56:12 NDF TC = 01;00;00;00 DF TC
90 35mm feet = 1 minute = 01;00;02 drop frame timecode

1 foot = 16 frames in 35 mm = 40 frames in 16 mm
3 35mm feet @ 24 fps = 2 seconds in real time
3 16mm feet @ 24 fps = 5 seconds in real time


Many sound editors use the Frame Master II calculator for doing conversions like these.
They're available here.

FreeTime, a freeware film/timecode calculator for Palm handhelds.
It's available here.


 R.J. Kizer is a sound editor currently practicing his mathematical prestidigitation
at 20th Century Fox. His recent credits include
X-Men, Planet of the Apes and
Catch Me If You Can. He can be reached via email