What is 2:3 or 3:2 pulldown?

Classic pulldown distributes four progressive film frames over five interlaced video frame periods, or ten fields, in a repeating two-field and three-field cadence. It is used for 23.976-to-29.97 and historically 24-to-30 workflows.

Why is a target frame count rounded?

A duration multiplied by the target rate can produce a fractional frame count, but an encoded clip must contain a whole number of frames. The calculator shows the nearest whole frame and its timing error.

Does a conform change audio pitch?

If audio is sped up or slowed down with the picture and no pitch correction is applied, its pitch changes. The estimate is 12 times log base 2 of the speed ratio, measured in semitones.

Does this calculator inspect or upload my media?

No. It uses the rates and length you enter, performs all calculations locally in the browser, and does not upload a clip or send production values to a backend.

Frame Rate Conversion Calculator — Speed Change, Conform & Pulldown

Compare two ways of moving footage between frame rates. An every-frame conform changes playback speed and duration; a standards conversion preserves duration and changes the target frame count. Exact 24000/1001, 30000/1001, and 60000/1001 rates are kept separate from rounded decimal rates.

Conversion inputs

Source frame rate

Use the clip or image-sequence rate.

Target frame rate

Use the timeline, playback, or delivery rate.

Clip length input

Source frame count

Enter a whole number from 1 to 999,999,999,999,999 frames.

Calculations, copying, and report creation stay in your browser. No media or entered production values are uploaded.

Conversion results

Every-frame conform —

Conformed duration—

Duration change—

Uncorrected audio pitch—

Source running time—

Duration-preserving frames—

Nearest-frame timing error—

Cadence analysis Enter valid values to compare the two workflows.

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How to use the frame-rate conversion calculator

Select the real source rate. Choose 23.976 for 24000/1001 media, not 24, unless the source is genuinely 24.000 fps.
Select the target rate. This can be the rate used to reinterpret the frames, the timeline rate, or the required delivery rate.
Enter the clip length. A frame count is exact. A duration is converted to the nearest possible complete source frame, and the quantization is disclosed.
Choose the result that matches the workflow. Use the conform result when every source frame will play once at the target rate. Use the duration-preserving result when running time must stay unchanged.

Conform and duration-preserving conversion formulas

Let S be source fps, T be target fps, and F be the integer number of source frames.

Source duration = F ÷ S Conform speed = (T ÷ S) × 100% Conformed duration = F ÷ T Duration-preserving target frames = F × (T ÷ S) Pitch shift without correction = 12 × log₂(T ÷ S) semitones

A conform changes time because the same frames are presented at a different rate. A duration-preserving conversion instead needs a frame-sampling process. Depending on the software and settings, that process may drop or duplicate frames, blend adjacent frames, use interlaced-field cadence, or synthesize frames with optical flow. The calculator reports counts and timing; it does not predict the visual quality of a particular algorithm.

2:3 pulldown, 3:2 pulldown, and cadence ratios

The names 2:3 pulldown and 3:2 pulldown refer to the same alternating field cadence, with naming conventions differing by phase description. In the classic operation, four progressive source frames are distributed across five interlaced video frame periods, or ten fields. The exact 5:4 rate ratio appears for 23.976 → 29.97 and 24 → 30.

Exact 24.000 → 29.97 is not a 5:4 rate match. Traditional film-to-NTSC transfer first slows 24 fps by 0.1% to 24000/1001 and then applies pulldown. Conversely, a 4:5 ratio can identify a possible inverse-telecine workflow, but only if the source actually contains a recoverable pulldown cadence. A rate ratio alone cannot prove that.

Common frame-rate conversion examples

Source → target	Every-frame conform speed	Conform effect	Duration-preserving note
23.976 → 29.97	125%	25% faster; duration becomes 80% of source	Exact 5:4 ratio; classic 2:3 field pulldown is possible.
24 → 25	104.1667%	4.1667% faster; about +0.707 semitones	Common film-to-PAL speed-up when a conform is acceptable.
25 → 24	96%	4% slower; duration becomes 104.1667%	A duration-preserving conversion needs a 24:25 frame mapping.
29.97 → 23.976	80%	20% slower if conformed	4:5 inverse-telecine ratio candidate only when pulldown is present.
50 → 25	50%	Half speed with every frame retained	Duration-preserving conversion can select every second frame.
120 → 24	20%	5× slow motion with every frame retained	Duration-preserving conversion can select every fifth frame.

Workflow assumptions and limits

This calculator assumes constant-frame-rate media and treats a clip as an integer sequence of progressive frames for duration math. Pulldown notes describe rate relationships; they do not inspect field order, cadence phase, mixed cadence, duplicated frames, variable-frame-rate timestamps, drop-frame timecode labels, audio sample boundaries, or NLE metadata. Confirm the actual source rate and delivery specification before a conform, broadcast master, or sync-critical finish.

Frame rate conversion FAQ

What does conforming a clip to another frame rate do?

An every-frame conform plays each source frame once at the target rate. For example, conforming 25 fps frames to 24 fps makes the clip run at 96% speed and last about 4.1667% longer.

How is frame-rate conversion different from conforming?

A duration-preserving conversion keeps the running time and maps the pictures to a new frame grid by dropping, duplicating, blending, field-distributing, or interpolating frames. A conform keeps the frame sequence and changes running time.

Is 2:3 pulldown the same as 3:2 pulldown?

The terms usually describe the same alternating two-field/three-field telecine cadence, though the starting phase and naming convention may differ. Four source frames occupy five interlaced video frame periods.

Is 23.976 exactly the same as 24 fps?

No. This calculator represents 23.976 as the exact rate 24000/1001, approximately 23.976023976. Over long programmes, treating it as 24.000 creates a meaningful timing difference.

Why can the duration-preserving target frame count have a decimal?

The mathematically exact count may fall between frame boundaries. Since a file contains a whole number of frames, the calculator also gives the nearest integer and the resulting timing error.

Will audio pitch always change during a conform?

Only if the audio speed follows picture speed without pitch correction. Many editing and finishing systems can preserve pitch, replace the production audio, or use a separate resampling workflow.

Does the calculator upload my clip or inputs?

No. It does not open media files. All rate, duration, copy, and report calculations run locally in the browser.

Production references

Adobe After Effects: importing and interpreting video and audio — describes 3:2 pulldown, four-to-five frame mapping, field cadence, and 29.97/23.976 removal.
Apple Final Cut Pro: conform frame sizes and rates — explains duration-preserving frame sampling, nearest-frame selection, blending, and optical flow.
Apple Final Cut Pro: change clip speed — describes automatic speed playback that retains every source frame at the project rate.